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LECTURE-NOTES 

ON 

CHEMISTRY 

FOR 

DENTAL STUDENTS 



INCLUDING 

DENTAL CHEMISTRY OF ALLOYS, AMALGAMS, ETC. 
SUCH PORTIONS OF ORGANIC AND PHYSIOLOGICAL CHEMISTRY AS 

HAVE PRACTICAL BEARING ON THE SUBJECT OF DENTISTRY 

AN INORGANIC QUALITATIVE ANALYSIS WITH SPECIALLY ADAPTED 

BLOWPIPE AND MICROSCOPICAL TESTS, AND THE CHEMICAL 

EXAMINATION OF URINE AND SALIVA 



& 



BY 



Hf CARLTON SMITH, Ph.G. 

LECTURER ON PHYSIOLOGICAL AND DENTAL CHEMISTRY AT HARVARD UNIVERSITY 

DENTAL SCHOOL; HONORARY MEMBER OF AMERICAN ACADEMY OF DENTAL 

SCIENCE, 1906; OF THE METROPOLITAN SOCTETY OF MASSACHUSETTS 

STATE DENTAL ASSOCIATION, I907; OF HARVARD DENTAL 

ALUMNI, 1 9 IO; AND NORTHERN OHIO DENTAL 

ASSOCIATION, 191 2 

SECOND EDITION REVISED AND ENLARGED 



FIRST THOUSAND 



NEW YORK 

JOHN WILEY & SONS 

London: CHAPMAN & HALL, Limited 

1912 






Copyright, 1006, 191 2, 

BY 

H. CARLTON SMITH 



Stanbopc jpress 

F. H.GILSON COMPANY 
BOSTON, U.S.A. 



©CLA327725 



PREFACE TO FIRST EDITION. 



The arrangement of this book follows rather closely the 
lecture course in Dental Chemistry as given by the author at 
the Harvard Dental School. It has been the aim of these 
lectures to give the student, as concisely as possible, such por- 
tions of the various branches of chemistry as are most likely 
to be of value in practical work. 

Simplicity of manipulation has in some cases been con- 
sidered of greater practical value than extreme accuracy, es- 
pecially in the chapter on Quantitative Analysis, the volumetric 
processes being given, as a rule, rather than the more exact but 
more difficult gravimetric methods. 

The usual equipment of a dental laboratory has been borne 
in mind, and considerable prominence given to the simpler 
analytical tests made in the dry way by means of few reagents. 

Recent text-books and current literature have been very 
generally consulted. New tests have been verified so far as 
possible — often modified — before being recommended to the 
student. 

The U. S. Dispensatory and the Newer Materia Medica, as 
given in the Druggists' Circular, have been drawn upon in the 
sections on Local Anaesthetics and Hall 's and Essig's Chemistries 
in the section on Alloys and Amalgams. 

A chapter on Organic Chemistry has been introduced, de- 
signed to furnish an understanding of this branch of chemical 
science, which will enable the student to better comprehend 
the physiological chemistry which follows. 

The chapter on the Analysis of Saliva is one which is, of 



IV PREFACE TO FIRST AND SECOND EDITIONS 

necessity, incomplete and imperfect. The investigations being 
at present carried on along the lines suggested by Dr. Joseph 
Michaels of Paris and Dr. Kirk of Philadelphia are opening up 
fields of research of the greatest magnitude and of utmost im- 
portance, and they can only be touched upon in this work. 

The atomic weights given are from the international atomic 
weights for 1905. = 16. 

In the chapter on Physiological Chemistry the author wishes 
to particularly acknowledge his indebtedness to Professor Wm. 
B. Hills of the Harvard Medical School, who furnished the 
majority of the laboratory experiments for this portion of the 
work. 

H. C. S. 

PREFACE TO SECOND EDITION. 



The second edition of Chemistry for Dental Students is an 
almost new book, using the first edition as foundation only. 

The chapter on Organic Chemistry has been considerably 
enlarged. 

A number of new cuts, about ninety pages of text, and eighty- 
five experiments have been added, and the arrangement has been 
changed with the purpose of making the book useful to any 
teacher of Dental Chemistry. The laboratory work follows 
closely the outline of lectures. 

An effort has been made to make the chapter on Saliva fairly 
complete to date, June, 191 2, but of course every month brings 
its added contribution of experiment and much of valuable fact 
relative to this interesting and important subject. 

The author wishes to acknowledge indebtedness to F. M. 
Rice, A.M., of the Chemical Department of Harvard Dental 
School for reviewing manuscript. 

H. C. S. 



TO THE STUDENT. 



As the student of dentistry takes up the study of chemistry, 
it is necessary that he should realize that the course will be of 
value to him in the ability acquired to draw correct inferences 
from observed phenomena, and in the attainment of accuracy 
and delicacy in manipulation, fully as much as in amount of 
chemical knowledge obtained. In other words, he must do his 
own thinking, carry out his own processes and experiments, 
make his own analyses, or the time spent will be little better 
than wasted, for the chemical facts which he may happen to 
remember will be of slight benefit in the work to which every 
student, worthy of the name, aspires, that of developing, 
broadening, and elevating the profession which he has chosen 
as his own. 

The course of study outlined in this book is designed to 
furnish the starting-points, which will be of practical value in 
solving the problems constantly presenting themselves for con- 
sideration in the various branches of chemistry. It is hoped 
that these starting-points may, in the future, serve as the basis 
for work along the lines of original research and that the best 
interests of dental science may be furthered thereby. 

It is supposed that the student has had the advantage of a 
laboratory training in general chemistry and is conversant 
with the properties and methods of preparation of the so-called 
non-met allic elements, also with the fundamental principles 
and laws of theoretical and physical chemistry, that he is 
familiar with laboratory apparatus, such as test-tubes, beakers, 
crucibles, casseroles, evaporating-dishes, retorts, etc., and that 



VI TO THE STUDENT 

he has had some experience in the ordinary processes of pre- 
cipitation, filtration, evaporation, distillation, sublimation, and 
crystallization. 

If there is any feeling of insufficient preparation it is strongly 
advised that a short course of preliminary study be taken. 
Chemistry furnishes the groundwork of all branches of medical 
science to a much greater extent than we are apt to think, 
and even in the study of subjects which in times past have 
been carried on with little reference to chemistry, we now see 
the desirability if not the necessity of a good general knowl- 
edge of chemical science. The physiologist and the bacteriolo- 
gist are to-day turning to chemistry for the utlimate solution 
of their most perplexing problems. 

H. C. S. 



TABLE OF CONTENTS. 



Page 

Title Page i 

Preface to First Edition iii 

Preface to Second Edition v 

To the Student . vi 

PART I. 
QUALITATIVE ANALYSIS. 

Chapter 

I. Introduction i 

II. Metals and Their Salts n 

III. Metals of Group One 14 

Analysis of Group One 19 

IV. Metals of Group Two 21 

Special Tests for Arsenic ; 28 

Analysis of Group Two 37 

V. Metals of Group Three 43 

Analysis of Group Three 47 

VI. Metals of Group Four 51 

Analysis of Group Four 55 

VII. Metals of Group Five 59 

Analysis of Group Five 64 

VEIL Metals of Group Srx 69 

Outline Scheme for Analysis 82 

IX. Analytical Reactions of the Acids 85 

X. Analysis in the Dry Way 96 

PART II. 
DENTAL METALLURGY. 

XI. Properties of the Metals 105 

XII. Alloys 108 

XIII. Amalgams 112 

XIV. Dental Cements 120 

XV. Fusible Metals and Solders 126 

XVI. Recovery of Residue 133 

vii 



Viii TABLE OF CONTENTS 

PART III. 

VOLUMETRIC ANALYSIS. 

Chapter Page 

XVII. Standard Solutions 137 

Quantitative Analysis of Dental Alloys 157 

PART IV. 

MICROCHEMICAL ANALYSIS. 

XVIII. Methods 159 

XIX. Local Anaesthetics 164 

XX. Teeth and Tartar 178 

PART V. 

ORGANIC CHEMISTRY. 

XXI. The Hydrocarbons and Substitution Products 181 

XXII. Alcohols 195 

XXIII. Ethers 204 

XXIV. Organic Acids 212 

XXV. Amins or Substituted Ammonias 226 

XXVI. Cyanogen Compounds 228 

XXVII. Urea 232 

XXVIII. Closed-chain Hydrocarbons 240 

PART VI. 

PHYSIOLOGICAL CHEMISTRY. 

XXIX. Ferments or Enzymes 253 

XXX. Carbohydrates 258 

XXXI. Fats and Oils 267 

XXXII. Proteins 270 

Simple Proteins 278 

Conjugated Proteins 285 

Derived Proteins 291 

Blood and Muscle 294 

PART VII. 
DIGESTION. 

XXXIII. Properties and Constituents of Saliva 302 

XXXIV. Analysis of Saliva 314 

Crystals from Dialyzed Saliva 326 

Tests for Abnormal Constituents 329 



TABLE OF CONTENTS LX 

Chapter Page 

XXXV. Gastric Digestion 331 

XXXVI. Pancreatic Digestion and Bile 337 

PART VIII. 
URINE. 

XXXVII. Physical Properties of Urine 343 

XXXVIII. Normal Constituents 348 

XXXIX. Abnormal Constituents 358 

Urinary Sediments 367 

Interpretation of Results 372 

Appendix 377 



DENTAL CHEMISTRY 



PART I. 

SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



CHAPTER I. 
INTRODUCTION. 

Every science has a language peculiar to itself, a thorough 
understanding of which is an essential preliminary to the study 
of that science. Hence, before we take up the study of Dental 
Chemistry, it will be well to review a few definitions and per- 
haps a few of the facts of Physics which are closely related to 
our subject. 

Elements. — An element is one of the simplest forms of 
matter — a substance which cannot by any means be resolved 
into matter differing from itself. 

Compounds. — Compounds consist of two or more elements 
chemically combined. 

Molecule. — The molecule is the smallest particle of matter 
that can exist and retain the properties of the original sub- 
stance. 

Atoms. — Atoms are the smaller particles of matter of which 
molecules are composed. 

Statements regarding the size and shape of atoms or mole- 
cules are statements of theories, which are helpful in under- 
standing certain chemical phenomena and some of which will 
be briefly considered in a subsequent lecture. 



2 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Chemical Affinity or Chemism is the attraction existing be- 
tween atoms whereby they are held together as molecules. 

Valence. — Valence is a property of atoms and represents 
their combining power relative to hydrogen. Valence is not 
always constant for the same elements; for example, sulphur 
has a combining power of six in sulphuric acid, of four in sulphur 
dioxide, and of two in hydrogen sulphide. Nitrogen has a com- 
bining power of three in ammonia gas and five in ammonium 
chloride. Valence is also indicated by the terms quanti valence 
and atomicity. 

Bond. — The bond is used to indicate the relationship of 
atoms in a molecule and at the same time shows the valence of 
the atom. 

Example, H — — H, the dash (bond) shows that oxygen 
has two combining points relative to the hydrogen which is 
considered to have one. 

Symbols. — Symbols are used to designate the various ele- 
ments. In some cases the initial letter of the element alone is 
used, as C for carbon. In other cases there is added a dis- 
tinctive small letter of the name when there happen to be a 
number of elements with names beginning with the same letter 
such as Calcium, Ca; Cobalt, Co; Copper, Cu; etc. 

Chemical Formula. — A chemical formula represents the 
molecule and is made up of the symbols of the several con- 
stituent elements. Chemical formulae may be empirical, dua- 
listic or graphic. The empirical formula represents the molecule 
without reference in any way to its structure, i.e., H 2 S0 4 . 

The dualistic formula indicates compounds which may enter 
into the composition of a molecule. By this sort of formula 
sulphuric acid would be represented by H 2 O.S0 3 . 

The graphic formula attempts to show the probable relation 
of the atoms in the molecule by means of bonds, e.g., 

H-O^O 
H-0 7 ^O 



INTRODUCTION 3 

Ions. — The electrically charged particles or parts of mole- 
cules capable of attraction to either cathode or anode in the 
process of electrolysis have been called " ions " (Faraday's 
definition). Ions may consist of single atoms as in H + CF or 
of groups of atoms (radicals) as in water H + (OH)~ or ammo- 
nium hydrate (NH 4 ) + (OH) _ . 

Acid. — An acid is a compound containing positive hydro- 
gen ions which may be replaced by a metallic element or radical. 
The more common acids are sour to the taste and act in char- 
acteristic manner upon a number of color compounds known as 
indicators. 

Base. — A base is a substance containing negative hydroxyl 
ions which may be replaced by acid radicals. Bases in general 
characteristics oppose acids. The strongest bases are known as 
alkalies, e.g., KOH, NaOH. 

A Salt. — A salt is a substance produced by the chemical 
union of an acid and a base. 

In the formation of the salt the acid may not have been 
completely neutralized by the base and an acid salt results. 
In such a case the salt contains a part of the hydrogen ions of 
the acid, e.g., potassium acid sulphate, KHS0 4 , the production 
of which may be represented by the equation 

KOH + H 2 S0 4 = KHSO4 + H 2 0. 

Acid salts may or may not have acid properties such as sour 
taste and power to give acid reactions with indicators. A salt 
may on the other hand be basic and contain a portion of the 
hydroxyl ions (or sometimes oxygen atoms) of the base. 

Example: Bi(OH) 3 + 2 HN0 3 = BiOH(N0 3 ) 2 + 2 H 2 or 
BiCl 3 + H 2 = BiOCl + 2 HC1. 

If the acid is exactly neutralized by the base, neutral salts result. 
2 NaOH + H 2 S0 4 = Na 2 S0 4 + 2 H 2 0. 



4 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Reactions between chemical substances may be " completed " 
or " reversible." 

A completed reaction is one which progresses in a definite 
way irrespective of changes in temperature or of the quan- 
tities of the reacting substances; or, a completed reaction is 
one in which one of the products is chemically inactive. This 
inactivity may be due to one of several causes, such as the pro- 
duction of an insoluble precipitate; e.g. AgCl in the reaction, 
AgN0 3 + NaCl = AgCl + NaN0 3 , 

or the escape of the product as a gas and its consequent re- 
moval from solution — as when carbonates are dissolved by acid. 
The reversible reaction is one in which the products remain 
to a greater or less degree in solution and a change of temper- 
ature or increase in quantity of one of the products may start a 
reverse reaction; for example, at the body temperature, dibasic 
sodium phosphate and uric acid may become monobasic sodium 
phosphate and acid sodium urate, 

Na2HP0 4 + H 2 U = NaH 2 P0 4 + NaHU, 
while at reduced temperature, 

NaH 2 P0 4 + NaHU = Na 2 HP0 4 + H 2 U. (See page 237.) 

Reversible reactions are often expressed by use of the sign 
<=>; thus, MgCl 2 + 2 NH 4 OH ^ Mg(OH) 2 + 2 NH 4 C1. The 
reaction may be expressed as an equation if we know what sub- 
stances take part in the reaction and what products are formed. 
The above reaction can be balanced at a glance and is therefore 
not well suited for illustration but the use of a little more com- 
plex equation will show how easily it can be balanced by a few 
algebraic combinations. 

Cu + HNO3 = Cu(N0 3 ) 2 + NO + H 2 0. 
Represent these all as unknown quantities. 

x Cu + y HNO3 = z Cu(N0 3 ) 2 +rn~NO+p H 2 0, 
then 



INTRODUCTION 



X Cu = Z Cu 
y H = £ H 2 

y N = z (N) 2 + w N 
3>0 3 = z(0 3 ) 2 + mO + pO 



x = z (i) 

y = 2 p (2) 

3; = 2 z + w (3) 

$y = 6z + m + p (4) 

multiplying equation 3 by 3, 33/ = 62 + 3^ (5) 

and by elimination (4 and 5) 2 m = p (6) 

and 4m = 2 p, then by eq. 2 y = 4m (7) 

assuming that m = 1, then, in 7, 3/ = 4; in 6, p = 2; in 3, 2 z = 3, 
or « = ij, in 1, « = i|. Knowing that all equations must be 
expressed by whole numbers we double these values and have 
x = 3,y = 8,z = 3,w = 2,p = 4. 

Upon substituting these values we shall find that the equa- 
tion " balances." 

Solution. — If we are to study physiological chemistry a 
clear understanding of the meaning of this term is desirable. 

" Solution is the equal distribution of a body in a liquid, 
the resulting mass being in all parts homogeneous and fluid 
enough to t form drops," according to an old definition quoted 
in " Colloids and the Ultra-microscope " by Dr. Richard Zsig- 
mondy. 

We can readily adopt this definition for present use pro- 
vided our conception of homogeneity is sufficiently elastic to 
include " Colloidal " solutions, which as a class are of rapidly 
increasing importance. 

The colloids are distinguished from crystalloids by their in- 
ability to pass through parchment membrane. In colloidal 
solutions the substance (colloid) may be considered as in 
suspension or a state of subdivision so nearly complete as 
to approach closely to the homogeneity of crystalloidal solu- 
tion. 

In many colloidal solutions the particles are large enough to 
interfere with the passage of light and the preparation is more 
or less opaque. In some, however, this is not noticeable except 
by use of polarized light and special apparatus. 



6 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

There is no sharply defined line between the suspensions and 
the colloidal solutions, and it is often true that the homogeneity 
of a solution is dependent upon the " grossness of our means of 
observation." The separation of the solid particles from the 
liquid may be effected in several ways. 

Sedimentation serves to remove the coarser particles from 
suspension: the liquid in this case may be decanted or turned 
off from the heavy sediment. 

Filtration through paper will remove the finer particles of 
suspension or ordinary precipitates. 

Some very fine precipitates, such as sulphur and barium sul- 
phate, require special papers. 

Colloidal substances as a class may be separated from the 
crystalloids by Dialysis, animal membrane suspended in dis- 
tilled water being used as a separating medium. The crystal- 
loids will pass through the membrane into the pure water, while 
the colloids remain behind. The use of the dialyzer as applied 
to saliva analysis is shown on page 327. 

Osmosis signifies the passage of water only through a mem- 
brane, tending to correct inequalities of pressure produced by 
differences in molecular concentrations of two solutions. 

This is usually illustrated by dropping potassium ferro- 
cyanide solution into copper sulphate. The drop of potassium 
ferrocyanide becomes surrounded by a film of copper ferro- 
cyanide, through which water alone will pass. Membrane of 
this character is known as semi-permeable. 

Porous cups are prepared for demonstrations of osmosis by 
precipitating within the pores of the cup or cell the ferrocyanide 
of copper. 

Osmotic pressure is the pressure produced within a semi- 
permeable cell by passage of water from the outside; or, as 
stated by Holland, it is " That push of the molecules of a solute 
upon its solvent which causes a flow through a membrane into 
the solution." 



INTRODUCTION 7 

Measures. — The metric system of weights and measures 
and the centigrade thermometer are largely used in all scien- 
tific work. The dentist, however, has also considerable use 
for troy weights and apothecaries' measures if he considers at 
all the composition of his gold solders, dental alloys, mouth 
washes, local anaesthetics, etc. Hence, a few equivalents are 
here given. 

The metre is the primary unit of the metric system and was 
originally calculated as one ten-millionth part of the quadrant 
from the equator to the pole. 

i metre = ioo centimeters = iooo millimeters or 39.37 
inches. 

1 centimeter = 10/25 or 0.3937 of an inch. 

1 cubic centimeter = 16.23 minims or 0.0338 of a fluid ounce. 

1000 cubic centimeters (c.c.) 1 liter or 2. 113 pts. 

The weight of 1 c.c. of pure water at the temperature of its 
greatest density (4 C.) is taken as a unit of weight and called 
a gram (gramme). 

1 gram = 15.43 grains. 

1000 grams = 1 kilogram (kilo) =35 oz. 120 grains or 
2.2 lbs. avoir. 

1 inch = 2.54 centimeters or 25.4 irullimeters. 

1 oz. av. = 28.3495 grams or 437.5 grains. 

1 fluid oz. = 8 fluid drams, 29.57 c - c -> or 45^ grains of water. 

1 fluid dram = 3.7 c.c. 

1 troy oz. = 8 drams (3) or 480 grains. 

1 troy oz. = 24 scruples (9) or 20 pennyweight (pwt. 
or dwt.) 

1 scruple = 20 grains, 1 pennyweight = 24 grains. 

1 grain = 64 milligrams. 

1 pint = 473.11 c.c. 

1 gallon = 8 pints, or 3785 c.c, or 231 cubic inches. 

1 lb. avoir. = 7000 grains or 453.59 grams. 



8 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Measure of Temperature. — We shall constantly meet ref- 
erence to both the Centigrade and Fahrenheit scales and an 
understanding of the relationship of the two methods is 
essential. 

The thermometer is graduated by marking the point at 
which the mercury stands when the instrument is placed on 
melting ice; and again the point reached by the mercury when 
the thermometer is surrounded by dry steam under ordinary 
atmospheric conditions. 

On the Centigrade thermometer, the lower or freezing point 
is marked o, the upper or boiling point is marked ioo, and the 
intervening space divided into ioo equal degrees. On the 
Fahrenheit scale, these points are marked respectively 32 and 
212 and the scale is divided into 180 ; hence, i° C. equals i.8° 
or 9/5 Fahrenheit, and i° F. equals 5/9 of a Centigrade degree. 
Providing for the different freezing points (o° and 32 ), we can 
formulate a rule for converting temperature records from one 
scale to the other, as follows: 

To convert Centigrade to Fahrenheit, take 9/5 of the given 
number of degrees and add 32. 

To convert Fahrenheit to Centigrade, subtract 32 from the 
given number and take 5/9 of the remainder; e.g. 

20 C. = 68° F. 
-5°C. =+2 3 °F. 
77 F. = 25 C. 
14 F. =-io°C. 

Absolute Temperature. 

According to the Law of Charles or of Gay-Lussac, gases 
(free molecules) contract 1/273 °f their volume, measured at 
o° C, for every Centigrade degree that the temperature falls; 
so it is assumed that, at a point 273 below the Centigrade zero, 
no further contraction would be possible, molecular motion 



INTRODUCTION g 

would cease and all things become solid. This temperature 
has been called the absolute zero and temperature recorded 
from this point absolute temperature; thus, water freezes at 
2 73 C. absolute temperature. 

Gravity Signifies Weight. 

Specific gravity is the relative weight of equal bulks of 
different substances, one of which is taken as a standard. 

The standard is usually water for liquids and solids. 

The standard for gases may be air or hydrogen. 

When gases are referred to hydrogen as a standard, the term 
density is often used instead of specific gravity, and, to avoid 
confusion, this usage is recommended; i.e., the density of carbon 
dioxide is 22, while its specific gravity compared with air is 
about 1.53. 

The density of a gas will, according to the Law of Avogadro r 
be one-half its molecular weight. 

The specific gravity of a liquid may be diminished by the 
solution of a gas, as in case of solution of ammonia; or it may 
be increased, as in case of solution of hydrochloric acid. Specific 
gravity is increased by solution of solid substances. 

The boiling point of a liquid is raised by the solution of 
solids. 

The freezing point of water is lowered by solution of either 
solids or gases. 

Cryoscopy is a term applied to the determination of freezing 
points in their relations to conditions of concentration or of 
purity. In medicine, the body fluids, such as blood, milk, and 
urine, have been investigated in this way. 

Precipitation signifies throwing out in solid form a substance 
previously held in solution. 

Precipitation may be brought about in three ways: 

First, by change of temperature, many substances being solu- 
ble at high temperature which will precipitate as the solution cools. 



IO SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Second, by change in the character of the solvent; example, 
laboratory exercise i, experiments i and 2. 

These two may be regarded as physical methods, while the 
third is chemical and involves the production of a new and 
comparatively insoluble substance: example, laboratory exer- 
cise 1, experiments 5 and 7. 

An old law of precipitation is, in effect, as follows: whenever 
two substances in solution can, by an interchange of radicals, 
produce a soluble and an insoluble, or a soluble and a less solu- 
ble substance, double decomposition always takes place and the 
less soluble substance will be precipitated. 

Laboratory Exercise I. 

Conditions Influencing Precipitation. 

Write Reactions if possible. 

Exp. 1. Mix equal volumes of an alcoholic solution of 
camphor and water. Explain precipitation. 

Exp. 2. To concentrated HC1 add a saturated solution of 
NaCl. Explain precipitation. 

Exp. 3. To 2 c.c. of HgCl 2 solution, found on side shelf, add 
2 c.c. of KI solution. 

Exp. 4. To 2 c.c. of HgCl 2 used above add 5 c.c. of KI solu- 
tion. 

Exp. 5. To a mixture of CuS0 4 and CdS0 4 add H 2 S water 
and filter. To the nitrate add more H 2 S water and filter again 
if precipitate forms. Repeat till no further precipitation takes 
place. 

Exp. 6. To a few cubic centimeters of strong HC1 add one 
drop of AgN0 3 solution. 

Exp. 7. To a few cubic centimeters of dilute HC1 add one 
drop of AgN0 3 solution. 

Exp. 8. Mix strong HN0 3 and H 2 S water. 

Exp. 9. Mix (NH 4 ) 2 S X solution and HC1 concentrated. 



CHAPTER II. 
THE METALS AND THEIR SALTS. 

Qualitative Analysis. 

The metals occur free in nature to quite an extent, but more 
often combined with other elements. These combinations are 
chiefly as oxids, sulphids, carbonates, and silicates, and in one 
or more of these four forms the great mass of metals contained 
in the earth's crust may be found. 

Metallic sulphates are found to a considerable extent. 

Other natural sources of the metals are phosphates and 
chlorids, also smaller amounts of nitrates and comparatively 
slight amounts of bromids, iodids, and fluorids. Metals are 
extracted from their ores chiefly by reduction with some form 
of carbon. In case of the oxids this reduction takes place directly, 
according to this reaction: 2 CuO + C = 2 Cu + C0 2 . 

In case the metallic combination is a sulphid, the ore is first 
" roasted" in the air, whereby the sulphur is burned off and an 
oxid, which may then be reduced as above, is formed: 
2 CuS + 3 2 = 2 CuO + 2 S0 2 . 

The native carbonates are reduced to oxids by calcination, as 
CaC0 3 + heat = CaO + C0 2 . 

The silicates must first be changed to carbonates by fusion 
with alkali carbonates ; then the reduction may be carried on as 
before: 

MgSi0 3 + Na 2 C0 3 = MgC0 3 + Na 2 Si0 3 ; 

then MgC0 3 + heat = MgO + C0 2 . 

The metals, from certain physical properties, have been vari- 



\: SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

ously classified. Thus, in the older books we read of the Noble 
metals, those unaffected by heat, as gold, silver, and platinum; 
the Base metals, the Bastard metals, those easily crystallizable, 
as antimony and zinc; the Metalloids, sodium and potassium. 

As the fact that the properties of metals were to a con- 
siderable extent dependent upon conditions of temperature and 
pressure became better understood, the old classifications were 
less and less used, until now we are very apt to group them 
according to the chemical behavior of their salts, irrespective 
of their properties as metals. Thus Ag, Pb, and Hg (Mercur- 
ous) form a group of metals whose chlorids are insoluble in 
water or dilute acids. These metals may consequently be 
thrown out of solution or precipitated by the addition of HC1 
to any solution of their salts. We therefore let Ag, Hg', and 
Pb constitute the First Analytical Group, and HC1 is the First 
Group Reagent. 

In like manner we find a group of nine metals that are pre- 
cipitated from dilute acid solution by hydrosulphuric acid 
(H 2 S). These metals are Cu, Cd, Bi, Hg, As, Sb, Sn, Au, and 
Pt, and constitute the Second Analytical Group, and H 2 S is the 
Second Group Reagent. 

The fact that the sulphids formed by the first four of these 
metals are insoluble in ammonium sulphid, and those formed by 
the last five are soluble, furnishes a simple method of separat- 
ing this group into two parts, a and b: 

Pb,* Cu, Cd, Bi, and Hg constituting Group II (a) and 

As, Sb, Sn, Au, and Pt, Group II (b). 

Thus, the metals are divided into various analytical groups, 
each with its own peculiar group reagent. Different groupings 
are possible, and hardly any two analysts will employ exactly 
the same scheme for identifying all the metals, although the 
following group divisions are generally used: 

* Lead is included in this group because it is not entirely separated as a chlorid 
in Group I, traces of it remaining in solution even after addition of HC1. 



THE METALS AND THEIR SALTS 13 

Analytical Groups. 

Group I. — Ag, Pb, and Hg'. Metals that form insoluble 
chlorids and are precipitated from aqueous solution by 
HC1 (the group reagent). 

Group II (a). — Cu, Cd, Bi, Hg", and Pb. Metals that form 
sulphids insoluble in dilute HC1 solution and also insoluble 
in ammonium sulphid. 

Group II (b) . — As, Sb, Sn, Au, and Pt. Metals that form 
sulphids insoluble in dilute HO but soluble in yellow 
ammonium sulphid, or alkaline hydrates. 

Group III. — Fe, Al, and Cr. In solutions free from H 2 S 
and which do not contain phosphates, oxalates, tartrates, 
or salts of certain other organic acids these three metals 
may be separated by ammonium hydrate, (NH 4 OH). 

Group IV. — Co, Ni, Mn, and Zn. Metals forming sulphids 
soluble in acid but insoluble in alkaline solution. Ammo- 
nium sulphid, (NH 4 ) 2 S, is the group reagent. 

Group V. — Ba, Sr, Ca, and Mg.* Metals forming car- 
bonates, insoluble in alkaline solutions. The group 
reagent is ammonium carbonate, (NH 4 ) 2 C0 3 . 

Group VI. — K, Na, Li, NH 4 . Metals which cannot be 
precipitated by any single reagent and for which it is 
necessary to make individual tests. 

It is our purpose to take up the study of the metals accord- 
ing to their analytical grouping: first, the deportment of their 
salts in solution; later, the metals themselves and their specific 
application to dentistry. 

* In the process of analysis, magnesium is held in solution by the presence of 
NH4CI and is not thrown out as a carbonate with the other three members of 
the group. 



CHAPTER III. 
METALS OF GROUP I. 

Silver, Ag (Argentum). 

The Metal. — Atomic weight 107.93. Silver occurs free, as 
sulphids, such as silver glance, Ag 2 S, and in combination with 
the sulphids of antimony, lead, and copper. 

It occurs also as silver chlorid, AgCl, known as "Horn 
Silver." 

Silver fuses at 954 C, forming a revolving globule on char- 
coal or plaster without oxidation. 

Silver dissolves in hot H 2 S0 4 with evolution of S0 2 . It is 
readily soluble in nitric acid with formation of AgN0 3 , colorless 
crystals, without water of crystallization. 

Silver amalgamates readily, and the " amalgamation process" 
is one of the important methods for its reduction from the ore. 

This process, briefly, is as follows: The ore is roasted with 
salt, producing chlorid of silver; this, in suspension in water, is 
reduced by metallic iron, 

2 AgCl + Fe = FeCl 2 + 2 Ag. 

The mixture treated with mercury forms an amalgam from 
which the mercury can be driven off by heat. 

Alloys. — Important alloys of silver are United States coin 
silver, consisting of silver 90 parts, copper 10 parts; and Sterling 
silver consists of silver 92.5 parts, copper 7.5 parts. Dental 
or amalgam alloys contain 50 to 65% silver. 

Compounds. — Salts of silver are liable to decomposition by 
action of light with reduction in greater or less degree to metallic 

14 



METALS OF GROUP I. 1 5 

silver. The salts change from violet to black according to the 
amount of silver reduced. Such reduction is used in the prep- 
aration and use of the ordinary photographic plates. 

Silver oxid (Ag 2 0), a dark brown powder, may be produced 
in the wet way, i.e., by precipitation of soluble silver salts with 
hydroxids of the fixed alkalis. 

2 AgN0 3 + 2 NaOH = Ag 2 + H 2 + 2 NaN0 3 . 

Silver hydroxid (white) may be formed if the above reaction 
is brought about in alcoholic solution; but it is a very unstable 
compound, quickly changing to Ag 2 + H 2 0. Silver thiosul- 
phate, Ag 2 S 2 3 , may be precipitated white from solution of silver 
nitrate and sodium thiosulphate. Excess of the thiosulphate 
produces a soluble double salt NaAgS 2 3 . This fact may be 
utilized in the removal of silver stains. 

Fused silver nitrate in the form of pencils or small sticks is 
used as an escharotic, and is known as " Lunar Caustic. " Dilute 
lunar caustic consists of equal parts of AgN0 3 and KN0 3 fused 
together in pencil form. 

Analytical Reactions. — Make the following tests with a 
weak solution of AgN0 3 (about 2%). Write the reactions and 
enter color and solubility of each precipitate formed in labora- 
tory note-book.* 

AgN0 3 with HC1 gives a white curdy precipitate of AgCl 
which darkens by action of sunlight. If Ag solution is very 
dilute, the precipitate will assume the curdy appearance and 
filter more easily if it is heated and rotated quite rapidly in 
the test-tube. Allow the precipitate to settle. Decant the 
liquid carefully, divide precipitate into two parts, and test its 
solubility in dilute nitric acid, also in ammonia water. 

* The author uses mimeograph copies of these experiments with space for the 
reactions and colors of precipitates, which are filled out without reference to the 
book and handed in by the student at the close of the laboratory exercise. 

These reactions have purposely been confined to such as may be applied to the 
process of analysis. 



16 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

AgN0 3 with KBr gives a white precipitate of AgBr, less 
easily soluble in ammonia than the AgCl. 

AgN0 3 with KI gives a pale yellow precipitate of Agl, 
insoluble in ammonia. 

AgNC>3 with H 2 S gives a black precipitate of Ag 2 S. AgN03 
with K 2 Cr0 4 gives a red precipitate of Ag 2 Cr0 4 in neutral solu- 
tion. Test the solubility of Ag 2 Cr0 4 in NH 4 OH, HC1, and 
HN0 3 . 

Mercury, Hg (Hydrargyrum). 

The Metal. — Atomic weight 199.8. Occurs as red sulphid, 
cinnabar, and in small quantities amalgamated with silver or 
gold or combined with chlorin or iodin. It is the only metal 
which is liquid at ordinary temperatures, solidifying at — 
39° C. 

It boils at 3 5 7. 8° C. and this wide range of temperature 
throughout which the fluid form is maintained, together with its 
comparatively great coefficient of expansion (about 1/160), 
makes it particularly suitable for use in thermometers and other 
instruments for measuring temperature or pressure. 

The molecule of mercury consists of a single atom. 

Alloys of mercury are amalgams and will be considered 
under this head. 

Compounds. — Mercury forms two series of salts; one, mer- 
curous salts referable to the oxide Hg 2 0, in which mercury 
exhibits a valence of one; and the other, mercuric, referable to 
HgO, the mercury having a valence of two. 

(Mercuric compounds will be considered under group two.) 

Mercurous chloride, or calomel, may be made by the reduc- 
tion of HgCl 2 by a reducing agent, as S0 2 . 2 HgCl 2 + 2 H 2 + 
S0 2 = 2 HgCl + H 2 S0 4 + 2 HC1; but the process commercially 
employed is usually to sublime a mixture of mercuric sulphate, 
sodium chloride and mercury. 

HgS0 4 + 2 NaCl + Hg = 2 HgCl + Na 2 S0 4 . 



METALS OF GROUP I. 17 

Mercurous iodide, Hgl, is a greenish colored unstable salt 
produced by double decomposition of HgN0 3 and KI. 

Mercurous nitrate is an easily soluble salt produced by 
action of cold nitric acid on excess of mercury, a solution of 
which may be used for the study of mercurous precipitates. 

Note. — The solution of mercurous nitrate, upon standing, will be found to 
contain more or less mercuric nitrate, unless care is taken to keep excess of mer- 
cury in the bottom of the bottle. 

Analytical Reactions. — HgN0 3 with HC1 gives a white pre- 
cipitate of HgCl (calomel). After the precipitate has settled, 
decant the liquid, and test the solubility of the HgCl in ammonia 
water. Does it dissolve? How does its behavior differ from 
that of AgCl? 

Alkaline hydroxids form with mercurous salts the black oxid 
Hg 2 0; a preparation of which, made with lime-water and calo- 
mel, is known as "blackwash. " 

Lead, Pb (Plumbum). 

The Metal. — Atomic weight 206.9. Melting-point from 
3 2 5 to 335 C. Occurs as sulphid (galena), PbS, in lesser quan- 
tities as native carbonate (cerussite), also as phosphate and 
chr ornate. 

Lead is reduced from the sulphid in a reverberatory furnace 
by a few simple reactions as follows: 3 PbS + 5 2 = 2 PbO + 
PbS0 4 + 2 S0 2 ; then, by increasing the heat without access of 
air, the sulphur is driven off and the lead separates by two double 
decompositions, 

2 PbO + PbS = 3 Pb + S0 2 and PbS0 4 + PbS = 2 Pb + 2 S0 2 . 

Lead is soluble in nitric or acetic acid, forming Pb(N0 3 ) 2 or 
Pb(C 2 H 3 2 ) 2 . 

Lead is also dissolved to a very slight extent by pure water 
containing oxygen, or by water containing C0 2 , mineral salts 



18 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

or organic matter. It tarnishes in the air, with formation of a 
suboxide, Pb 2 0. 

Alloys. — Solders and fusible metals are among the important 
alloys. 

Type metal consists of an alloy of lead and antimony. 

Compounds. — Besides the suboxide of lead above mentioned, 
three more compounds of lead and oxygen are of interest. 

Litharge, PbO, is the yellow oxide used in pharmacy as the 
base of "Diacylon plaster. " 

The black oxide, Pb0 2 , is used as an oxidizing agent. Red 
lead" (minium), Pb 3 4 , is practically a mixture of Pb0 2 and 2 PbO, 
and used as a source of Pb0 2 by treatment with HN0 3 . 

Pb 3 4 + 4 HNO3 = Pb0 2 + 2 Pb(N0 3 ) 2 + 2 H 2 0. 

Lead carbonate, as prepared by precipitation of soluble lead 
salts by alkali carbonates, has the composition (PbC0 3 ) 2 Pb(OH) 2 . 

The basic carbonate, prepared by exposure of the metal to 
fumes of acetic acid, C0 2 , and moisture, is known as "White 
lead, " and is used in manufacture of paint. 

Lead acetate, or sugar of lead, formed by solution of the 
metal or the oxide PbO in acetic acid, is a white soluble salt 
crystallizing with three molecules of H 2 0. The solution has an 
acid reaction to litmus paper. 

Lead subacetate, or basic acetate of lead, a solution of which 
is known as Goulard's extract, is made by boiling lead acetate 
solution with litharge. It is used in medicine as an external ap- 
plication and in physiological chemistry as a reagent. It deteri- 
orates by absorption of C0 2 and precipitation of a carbonate. 

Lead chromate (chrome yellow) is a yellow insoluble salt 
used as a pigment. 

Lead nitrate, an easily soluble white crystalline salt, may 
be used in the study of the analytical reactions of lead. 

Lead arsenate, a poisonous salt, is quite largely used for 
spraying trees. 



METALS OF GROUP I. 



19 



Analytical Reactions. — Pb(N0 3 ) 2 with 2 HC1 gives white 
precipitate of PbCl 2 . Test its solubility in hot water and in 
NH4OH. 

Pb(N0 3 ) 2 with NH4OH gives white precipitate of Pb(OH) 2 
insoluble in hot water. 

Pb(N0 3 ) 2 with H 2 S gives black PbS. Test solubility of 
precipitate in warm dilute HNO3. 

Pb(N0 3 ) 2 with H 2 S0 4 gives white precipitate of PbS0 4 , form- 
ing slowly in dilute solutions. 

Pb(N0 3 ) 2 with K 2 Cr0 4 (or K 2 Cr 2 7 ) gives a yellow pre- 
cipitate of PbCr0 4 . 

Pb(N0 3 ) 2 gives with KI a yellow precipitate, Pbl 2 . Avoid 
excess of the potassium iodid. 

By application of the reactions of the salts of Ag, Pb, and 
Hg', we may formulate a scheme for the separation and identi- 
fication of the metals of Group I as follows: 



Analysis of Group I. 

(Ag, Pb, Hg'.) 

To the clear solution to be tested add slowly dilute HO as 
long as any precipitation occurs. Filter and wash the precipi- 
tate once with cold water, add this washing to filtrate to be 
tested for remaining groups, then wash precipitate on the paper 
with several small portions of hot water. 



AgCl and HgCl remain undissolved. 



PbCl 2 is in the hot-water solution. 




Divide this hot-water solution into three parts and make 
three of the following tests for lead: First, with K 2 Cr 2 7 , which 




20 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

gives yellow precipitate of PbCr0 4 . Second, with dilute H 2 S0 4 , 
giving a white precipitate of PbS0 4 . Third, with H 2 S water, 
giving black precipitate of PbS. Fourth, with KI solution, which 
forms a yellow precipitate of Pbl 2 . Write these reactions. 

To undissolved residues of Hg and Ag chlorids add warm 
NH4OH. 

Hg remains on the paper, black, as HgNH 2 HgCl. 

Ag is dissolved by the NH 4 OH and may be precipitated 
as AgCl by adding HNO3 to acid reaction. Presence of 
Hg in the black residue may be confirmed as in Group II 
(page 38). 

QUESTIONS ON GROUP I. 

Why wash the precipitated chlorids only once with cold 
water ? 

Why is it necessary to wash the PbCl 2 out with hot water 
before using ammonia? 

Why is the ammonia used ? 

How does HNO3 reprecipitate silver chlorid? 

Laboratory Exercises II and III. 

Laboratory exercises 2 and 3 will consist of the analytical 
reactions of the first-group metals, a study of the solubility of 
the precipitates formed, and an analysis of an unknown solu- 
tion containing a mixture of first-group metals. 



CHAPTER IV. 
METALS OF GROUP II. 

Copper, Cu (Cuprum). 

The Metal. — Atomic weight 63.3. Melting-point 1054 C. 
Occurs free in vicinity of Lake Superior, also in western United 
States, Chili, and Spain, as sulphids, copper pyrites, CuFeS 2 , and 
copper glance, Cu 2 S. Malachite green and malachite blue are 
native basic carbonates of Cu. 

Copper dissolves easily in nitric acid and with difficulty in 
HO; heated with H2SO4 it forms CuS0 4 , with the evolution of 
S0 2 . 

Alloys of Copper are both numerous and important. The 
amalgam was formerly used in dentistry to a considerable 
extent. 

Copper is used to harden silver and gold, used in the manu- 
facture of coins, jewelry and the solders, and used in crown and 
bridge work. 

Copper is also used in the preparation of bronze, brass, bell 
metal, dental gold, and German silver. Page 108. 

Compounds. — Salts and solutions of copper are usually 
blue or green. 

Copper forms two series of salts : the cuprous, of which there 
are but few important compounds, and the cupric. Cuprous 
oxid, Cu 2 0, which is red in color (sometimes yellow through 
admixture of CuOH) and obtained by reduction of cupric salts 
by organic substances such as sugar, and cuprous chlorid, used 
as a reagent for the detection of acetylene, are perhaps the most 
important. 

21 



22 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Cupric oxid, CuO, is a black powder formed by ignition of 
copper in the air or by boiling copper solution with the fixed 
alkali hydroxids. 

Copper arsenate and aceto-arsenite, the latter known as 
Paris green, are both green powders which have been used as 
pigments and as insecticides. 

Copper sulphate, CuS0 4 , crystallizes with five molecules of 
water and is known as bluestone or blue vitriol. It is used 
extensively in the ''Gravity Battery," and in copper plating. 

Verdigris is a sub-acetate or oxy-acetate of copper composi- 
tion, CU 2 0(C2H 3 02)2. 

Copper salts combine with NH 3 , forming a series of "cupram- 
monium" compounds freely soluble and of intense blue color. 

The chlorid nitrate and sulphate are the common soluble 
salts. A i% solution of either of these will give the analytical 
reactions. 

Analytical Reactions. — CuS0 4 with H 2 S gives CuS, brownish- 
black sulphid. Test its solubility in (NH 4 ) 2 S and in warm dilute 
HN0 3 . 

CuS0 4 with NH 4 OH (one or two drops of reagent) will pre- 
cipitate Cu(OH) 2 bluish white. Add more NH 4 OH to same test- 
tube and note the result. To this clear solution add a sufficient 
amount of dry KCN to completely decolorize the liquid. Then 
add to the mixture some H 2 S water. Is the black CuS thrown 
out? The behavior of Cu solutions thus treated is due to the 
formation of double salts, the solution in ammonia being due 
to a compound of CuS0 4 and NH 3 , and the decolorization of the 
blue solution to one of Cu(CN) 2 and KCN. 

CuS0 4 with K 4 FeCy 6 (potassium ferrocyanid) gives in acetic 
acid solution a red-brown precipitate of Cu 2 FeCy 6 . 

Metallic zinc or iron will precipitate copper from solution. 
Hold a knife-blade in a solution of CuS0 4 for a few seconds. 



METALS OF GROUP II. 23 

Mercury in Mercuric Combination. 

Compounds of Dyad Mercury. — Mercuric oxid, HgO, is a 
red powder obtained by ignition of mercury in the air. Mer- 
curic oxid may also be prepared by precipitation of mercuric 
chlorid with alkaline hydroxids. A precipitate thus formed is 
yellow in color, and, when prepared by mixing mercuric chlorid 
and lime water, forms the "yellow wash" used to a considerable 
extent in pharmacy. 

Mercuric chlorid, HgCl 2 . This intensely poisonous salt is 
known by the fairly descriptive name of corrosive sublimate. 
It corrodes metals, such as zinc and iron; it coagulates albumin 
and acts as a corrosive poison when taken internally. 

It is made in a manner analogous to that used for the prepar- 
ation of calomel, i.e., by sublimation, the salts used in this 
instance being mercuric sulphate and sodium chlorid alone. 

Hg 2 S0 4 + NaCl = 2 HgCl + Na 2 S0 4 . 

Mercuric chlorid is antiseptic and a disinfectant in dilu- 
tions of 1 to 1000. Antiseptic tablets designed to give about 
this strength of solution by the addition of one tablet to one 
pint of water are made to contain 7.7 grains HgCl2 and 7.3 
grains NH 4 C1, with sufficient purple coloring to advertise the 
nature of the tablets and thus act as a safeguard against acciden- 
tal poisoning. 

Mercuric chlorid is soluble in water and in alcohol. It is 
used in the preparation of antiseptic gauze, sterile cotton, etc., 
but, on account of its corrosive properties, cannot be used to 
sterilize instruments. 

Ammoniated mercury, mercur-ammonium chlorid, or white 
precipitate (NH 2 HgCl) is a white powder obtained by slowly 
pouring a solution of HgCl 2 into ammonia water. 

Mercuric iodid, red iodid (Hgl 2 ), is made by reaction of 
mercuric chlorid with potassium iodid: 

HgCl 2 + 2 KI = 2 KC1 + HgL 



24 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Mercuric iodid is soluble in excess of either reagent, also in 
alcohol. 

Mercuric iodid combines with potassium iodid (KI) form- 
ing an iodo-hydrargyrate, used as a reagent in physiological 
chemistry (page 278), also as an alkaloidal precipitant. 

An alkaline solution of potassium iodo-hydrargyrate, con- 
stitutes Nessler's reagent, used in analysis of water and of saliva 
as a test for ammonium compounds. 

Analytical Reactions. — A 2% solution of corrosive sub- 
limate (HgCl 2 ) may be used in demonstrating the reactions of 
dyad mercury. 

HgCl 2 with H 2 S gives first a white precipitate, turning yellow, 
brown, and finally black, as proportion of H 2 S increases. The 
black precipitate only is mercuric sulphid, and care must be 
taken to add H 2 S till this compound is produced. 

Test the solubility of HgS in (NH 4 ) 2 S and HN0 3 . 

To HgCl 2 solution add SnCl 2 . The mercuric chlorid is re- 
duced to mercurous chlorid (HgCl, white) or metallic mercury 
(Hg, gray), according to proportion of the tin salt used: 

2 HgCl 2 + SnCl 2 = 2 HgCl + SnCU 
or HgCl 2 + SnCl 2 = Hg + SnCl 4 . 

HgCl 2 with KI gives red Hgl 2 , easily soluble in excess of 
either of the reagents. 

HgCl 2 with NH 4 OH gives white precipitate of (NH 2 Hg)Cl, 
known as " white precipitate" (see ammoniated mercury). 
"Red precipitate" is a term sometimes used to designate the 
red oxid of mercury, HgO, made in the dry way. 

Bismuth, Bi. 

The Metal. — Atomic weight 208.5; melting-point 268 C. 
At higher temperatures Bi burns to Bi 2 3 . Bismuth does not 
occur in large quantities, but is usually found in the free state. 



METALS OF GROUP II. 



25 



Small amounts are obtained from the oxid, Bi 2 3 , bismuth 
ochre, and from the sulphid, Bi 2 S 3 . 

It is easily identified by means of the blowpipe test on 
plaster with S and KI (page 102). 

Alloys. — The most important alloys from a dental stand- 
point are the fusible metals, Mellot's metal, Wood's metal, 
Rose's metal, etc. (page 126). 

Compounds. — Salts of bismuth as a rule require excess of 
acid for permanent solution; and, by adding a considerable 
volume of water, they are easily thrown out of solution as insol- 
uble basic or oxysalts, the reaction of the nitrate being as 
follows : 

Bi(N0 3 ) 3 + H 2 - BiON0 3 + 2 HN0 3 . 

This may be demonstrated by allowing a few drops of bis- 
muth solution to fall into a comparatively large amount of H 2 
(two to six ounces). A white cloud of insoluble oxysalt may 
be observed settling through the clear water. This may be em- 
ployed as a final test for Bi in the course of systematic analysis. 

The subnitrate and the subcarbonate of bismuth are both 
used in medicine. The latter is a common starting-point in the 
preparation of other bismuth salts. 

Analytical Reactions. — The most available salt is the 
nitrate, insoluble in water unless strongly acidulated. 

Use a 2% solution of Bi(N0 3 )3 in the following tests: 

Bi(N0 3 ) 3 with NH4OH gives white precipitate of bismuth 
hydroxid, Bi(OH) 3 . 

Bi(N0 3 ) 3 with H 2 S precipitates Bi 2 S 3 , brownish black, in- 
soluble in (NH 4 ) 2 S, but soluble in warm dilute HN0 3 . 

Cadmium, Cd. 
The Metal. — Atomic weight 112.4; melting-point 320 C. 
Occurs associated with Zn in zinc blende. It is more easily 
volatile than zinc, and advantage is taken of this fact in effect- 
ing its separation from that metal. 



26 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Alloys. — Cadmium is used as a constituent of fusible 
metals and rarely, in small proportion, in dental alloys. Its use 
in the latter case is objectionable on account of the yellow stain 
of CdS frequently produced (page 115, amalgam). 

Analytical Reactions. — A 2% solution of the sulphate or 
nitrate may be used in studying the deportment of cadmium 
salts. 

CdS0 4 with H 2 S gives a bright yellow sulphid, CdS, soluble 
in dilute nitric acid. 

CdS0 4 with (NH 4 ) 2 S also precipitates the yellow sulphid. 

Cadmium sulphid forms slowly, and, in presence of Cu or 
other second-group metals, may escape precipitation if the 
reagent is added in insufficient quantity. 

Arsenic, As. 

Atomic weight 75.0. Occurs associated with copper and 
iron sulphids, as arsenical pyrites, FeAs.FeS2; as native sulphids, 
orpiment, AS2S3, and realgar, As 2 S 2 ; also to some extent as the 
trioxid, As 2 3 . 

Compounds. — Arsenic forms two series of salts, the arseni- 
ous, As"', and arsenic, As v , and it also acts as an acid radical 
forming arsenious and arsenic acids. In the process of analysis, 
arsenic compounds whether acid or basic are reduced to arseni- 
ous by action of H 2 S. It is most easily obtained in the form 
of the trioxid, As 2 3 , also known as arsenious acid or white 
arsenic. 

White arsenic is intensely poisonous; but, nevertheless, it 
has been very freely used in curing the skin of fur-bearing 
animals and otherwise as a preservative. In dentistry white 
arsenic is used to devitalize pulp. 

Arsenic is widely distributed in nature, occurring in soft coal, 
from which source it finds its way into the roadside dust or 
any substance capable of holding dust, such as the majority of 
fabrics, wall papers, etc. Arsenic is a common impurity in 



METALS OF GROUP II. 27 

mercury, zinc, and commercial acids. Inasmuch as these things 
are largely used in the preparation of filling material used by 
dentists, it is necessary that considerable pains be taken to 
prevent the presence of the poison in sufficient quantity to 
cause irritation. 

The poisonous character of arsenic differs greatly with the 
combination in which it occurs. A gaseous hydrid of arsenic, 
AsH 3 , being among the most poisonous of its compounds, while 
some of the organic compounds are claimed to be non-poisonous. 

Arsenic forms an insoluble arsenate with ferric hydrate; 
hence, freshly precipitated ferric hydroxid is the official anti- 
dote for arsenical poisoning. This is prepared by mixing 150 c.c.. 
of dilute ferric sulphate solution (containing 50 c.c. of the U. S. P. 
" Solution") with a well-shaken mixture of 10 grains of oxid 
of magnesium in about 750 c.c. of water: 

Fe 2 (S0 4 ) 3 + 3 Mg(OH) 2 = Fe 2 (OH) 6 + 3 MgS0 4 . 

Fowler's solution containing 1% As 2 3 dissolved by use of 
potassium bicarbonate. Solution of arsenious acid containing 
1% As 2 3 dissolved by aid of two parts of HC1. Donovan's 
solution containing 1% each of Asl 3 and Hgl 2 , and Pearson's 
solution containing 1% sodium arsenate are Pharmacopceial 
preparations of arsenic. 

Analytical Reactions. — A solution for studying the reactions 
of arsenic (As'") is conveniently made by dissolving about 
15 grams of white arsenic in dilute NaOH solution by aid of 
heat, then diluting to one liter and acidifying slightly with 
HC1. 

To an arsenious solution, which may be represented by AsCl 3 , 
add H 2 S water. A lemon-yellow precipitate of As 2 S 3 will be 
thrown down. Test the solubility of this precipitate in yellow 
ammonium sulphid and in ammonium carbonate. 

To the alkaline solution of the sulphid add excess of HC1: 
As 2 S 3 is precipitated. 



28 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

To an arsenious solution add (NH^S in repeated small 
portions. 

In neutral solution, as of sodium arsenite, Na 3 As0 3 , silver 
nitrate will throw down yellow silver arsenite, soluble in excess 
of nitric acid or ammonia. 

SPECIAL TESTS FOR ARSENIC. 

Reinsch's Test for arsenic, applicable to any solution 
whether organic or not, and very valuable for a preliminary test, 
is made as follows: place the solution or mixture to be tested 
in a porcelain dish, acidify strongly with HC1, and add a small 
strip of bright copper foil (cleaned in dilute HN0 3 and thor- 
oughly washed in distilled H 2 0) and boil for ten or twenty 
minutes, adding sufficient water to replace loss by evaporation. 
Remove the copper foil; a dark gray to black coating is an indi- 
cation of arsenic but not conclusive, as some other substances 
give similar deposits, mercury and antimony in particular. 

To prove the presence of As roll the foil as tightly as possible 
and place it in the bulb of a small glass matrass (Fig. 1). 



Fig. 1. 

Heat the bulb over a very small luminous flame, when crys- 
tals of AS2O3 (tetrahedral or octahedral) will deposit in the con- 
stricted portion of the tube, and which may be identified by 
microscopical examination. There will be sufficient air in the 
matrass for the formation of the oxid and the test becomes much 
more delicate than if heated in the ordinary open tube as often 
recommended. 

Gutzeit's Test is made by placing the suspected solution 
in a test-tube, acidifying with H 2 S0 4 , adding a few small pieces 
of arsenic-free zinc, and, as hydrogen begins to be given off, 
placing over the mouth of the tube a piece of filter-paper carry- 



METALS OF GROUP II. 29 

ing a drop of a strong solution of AgN0 3 . The presence of 
arsenic is indicated by the darkening of the moistened filter- 
paper in accordance with the following reactions: 

The nascent H liberated by action of the Zn upon the acid 
forms with any As present the gaseous AsH 3 which, in contact 
with the filter-paper wet with AgN0 3 solution, produces a brown 
or black stain of metallic Ag, while the As becomes arsenious 
acid, H 3 As0 3 . The stain may possibly be yellow by forma- 
tion of a compound of silver arsenide and silver nitrate, but, as a 
rule, moisture is present in sufficient amount to insure the decom- 
position of this compound. 

Antimony will give a similar brown or black stain (not 
yellow), but presence of As may be conclusively demonstrated 
by making Fleitmann's Test, which is conducted in the same 
way as the preceding, except that the hydrogen is evolved in 
alkaline solution, either by means of Zn and strong KOH solu- 
tion (Zn + 2 KOH = K 2 Zn0 2 -f H 2 ) or by sodium amalgam 
(made with arsenic-free mercury) and water (NaHg x + H 2 = 
NaOH + Hg + H). In this case the SbH 3 is not formed; so a 
stain thus obtained constitutes a positive test for arsenic. 

The Marsh-Berzelius Test for arsenic is the most delicate 
of all and the one to which we resort in detecting As in the saliva 
or the urine. By this method one two-hundredth of a milligram 
or about 1/ 12800 of a grain can be easily shown as a brown 
deposit in the constricted tube at about the point K, Fig. 2. 
The apparatus used in this test is shown in Fig. 2, and consists 
of a small Erlenmeyer flask, or wide-mouth bottle, fitted as a 
hydrogen generator, A, and connected with a drying-tube, B, 
filled with fused calcium chlorid, then with a tube of hard glass, 
C, drawn out to a very small diameter for half its length. 

The generator A is charged with arsenic-free zinc, and dilute 
sulphuric acid (1/5) introduced through the thistle-tube E. 
After all air has been driven from the apparatus, light the escaping 
HatT, then the Bunsen burner D, and allow the generator to 



30 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



run for about twenty minutes, thus making a blank test of 
apparatus and reagents; if at the end of this time the hard glass 
is perfectly free from any deposit, the suspected liquid, which 
must have been freed from organic matter (process described 
in detail in chapter on Urine Analysis), may be introduced in 
portions of about 10 c.c. each. 

The flame should be spread somewhat so as to heat at least 
i inch of the glass tube. This may be accomplished, in the 




Fig. 2. 

absence of a burner- tip, by placing an inverted V-shaped piece 
of asbestos board, i inch wide, over the heated part of the tube. 

The presence of arsenic increases the evolution of hydrogen 
and, unless the solution is added gradually, the AsH 3 may be 
driven so rapidly past the flame as to escape decomposition, or 
the tube may become heated to such an extent that arsenic will 
not be deposited. 

The escape of As at T may be noticed by the bluish color of 
the flame and by the characteristic garlic odor. 

Antimony is similarly deposited as a dead-black stain in- 
stead of brown-black, and as Sb is less easily volatile than As 



METALS OF GROUP II. 



31 



the deposit will be nearer the flame, possibly on both sides of 
the flame. (For further differences between As and Sb see 
tests given on page 32.) 

A test, using an apparatus similar to the above and known 
as Gutzeit's test, has been investigated by Sanger and Black, 
(proceedings of the American Academy of Arts and Sciences, 
October, 1907). 

AsH 3 is produced in the generator by use of Zn and HC1, 
and passed through the drying tube B; (Fig. 2) then through 
a tube of uniform diameter C containing strips of drawing paper 
sensitized with solution of HgCl 2 . 

The HgCl 2 paper is stained yellow to brown beginning at 
the end next the generator, and by carefully regulating con- 
ditions, the extent of the stain may have a quantitative value. 

Arsenic compounds (As r ), as Na 2 HAs0 4 , are of but little 
interest from the dentist's standpoint. 

All arsenic compounds are reduced by nascent H to arsenious 
combinations, then to elementary As, then to AsH 3 (arsine); 
hence the special tests given for arsenious compounds are ap- 
plicable. 

Free chlorin, nitric acid, and potassium ferricyanid oxidize 
arsenious compounds to arsenic, and in this condition the As 
is not easily volatilized and organic matter may be destroyed 
by deflagration (in presence of excess of nitrates) with but 
slight loss of arsenic. 

Antimony, Sb (Stibium). 

Atomic weight 120.2. Occurs native in Australia, and as 
the sulphid, Sb 2 S 3 , known as stibnite. 

Alloys. — Antimony is used in making type metal, Britan- 
nia metal, and rarely in low-grade dental alloys. 

Compounds. — The salts of antimony may be classified as 
antimony salts, referable to the hydroxid Sb(OH)3, and anti- 
monyl salts, referable to SbO(OH) 3 . 



32 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Butter of antimony, antimony tri-chlorid, SbCl 3 , when 
pure, is a colorless solid of buttery consistency, hence its 
name. It may be formed by direct union of constituent 
elements. 

Salts of antimony tend to form oxycompounds and are held 
in solution by excess of acid. The antimonious chlorid, SbCl 3 , 
in solution with HC1 is precipitated by excess of water as a 
white oxychlorid, Sb 4 Cl20 5 , also known as "powder of Algaroth." 
The antimonic chlorid in like manner precipitates the anti- 
monic oxychlorid, SbOCl 3 . Demonstrate by turning i or 2 c.c. 
of SbCl 3 solution into a large excess of water. 

Analytical Reactions. — The most common compound of 
antimony is the double tartrate of antimony and potassium 
(KSbOC 4 H 4 6 ), known as tartar emetic (an antimonyl com- 
pound). A 2% aqueous solution may be used in the following 
tests : 

To an antimony solution represented by SbCl3 add H 2 S 
water: Sb 2 S 3 is precipitated orange-red. Test solubility of the 
precipitate in (NH 4 ) 2 S and in (NH 4 ) 2 C0 3 . 
How does it differ from arsenic ? 

Upon the addition of HC1 in excess to the 
ammonium sulphid solution the Sb is repre- 
cipitated, but not necessarily as Sb 2 S 3 , but 
more usually as Sb 2 S 5 or a mixture of the 
two sulphids. 

Marsh's test for As (or Sb) consists of a 
simple hydrogen generator with glass tip for 
burning the gas, as shown in Fig. 3. In this 
apparatus Sb and As are converted into the 
gaseous hydrides, AsH 3 and SbH 3 ; and, if a 
piece of cold porcelain is pressed down upon 
the flame, As or Sb will be deposited as 
metallic stains (mirrors) upon the porcelain. To distinguish be- 
tween As and Sb spots the following tests will suffice: 




Fig. 3. 



METALS OF GROUP II. 33 

Arsenic. Antimony. 

Brown-black, lustrous spots. Dead brown or black surfaces. 
Soluble in solution of hypo- Insoluble in solution of hypo- 
chlorite of lime or soda. chlorite of lime or soda. 
Easily volatilized. Volatilized at red heat. 

Antimony may be retained in the generator by the intro- 
duction of a piece of platinum-foil, the Sb being precipitated 
upon the platinum to which it adheres quite strongly. 

Tin, Sn (Stannum). 

The Metal. — Atomic weight 119.0; melting-point 238 C. 
Cassiterite, or tin-stone, nearly pure Sn02, is by far the most 
important source. The free metal has been found associated 
with gold. 

Banca tin from the East Indies and block tin from England 
are pure varieties of the commercial article. Pure tin will give 
a peculiar crackling sound when bent. Tin is very malleable at 
the ordinary temperature, being fourth in the list of malleable 
metals (see page 105), but becomes brittle when heated to about 
200 c 

Alloys. — Pewter usually contains Sn, Pb, Cu, and Sb, some- 
times Zn. Rees's alloy Sn 20 parts, gold 1 part, and silver 2 
parts. Tin is also a constituent of solders, fusible metals, 
Babbitt's metal, bell metal, and bronze. 

An alloy of tin and mercury (tin amalgam) is used for "silver- 
ing mirrors." 

Compounds. — Metallic tin is not dissolved by HN0 3 , but 
is converted into a white, insoluble metastannic acid. This 
acid, upon standing, changes to normal stannic acid which is 
easily soluble in acids; hence, in making use of this reaction in 
the analysis of amalgam alloys, it is not well to allow the nitric 
acid solution of the alloy to stand too long before filtering. 



34 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Metallic zinc thrown into a tin solution will precipitate the 
tin as follows: SnCl 2 + Zn = ZnCl 2 + Sn. 

This reaction is used in the separation of tin from antimony 
in the second group; and, in order to obtain the tin in soluble 
form suitable for a final test, it is necessary to add HC1 sufficient 
first to dissolve all the Zn present; otherwise it (Sn) may remain 
adhering to the zinc. 

Tin, like arsenic and antimony, forms two series of salts, the 
stannous (Sn") and the stannic (Sn IV ). A little HC1 treated 
with excess of granulated tin till hydrogen is no longer given off 
furnishes a solution of stannous chlorid suitable for the follow- 
ing experiments: 

Analytical Reactions. — SnCl 2 with H 2 S gives brown pre- 
cipitate of SnS, soluble in (NH 4 ) 2 S, insoluble in (NH 4 ) 2 C0 3 . 

SnCl 2 with HgCl 2 gives a white or gray precipitate, as ex- 
plained on page 24 under "Mercury," and is used as a test for 
presence of mercury. It may also be used as an alkaloidal pre- 
cipitant. 

Strong solutions of SnCl 2 in presence of metallic Sn keep 
fairly well, but dilute solutions without an excess of tin oxidize 
very rapidly to stannic combinations and cease to be of value 
as reagents. 

Gold, Au (Aurum). 

Atomic weight 197.2; melting-point 1075 C. Usually found 
uncombined, but mixed with various impurities. 

Alloys. — Gold is alloyed with copper to make it harder and 
more durable for use in the manufacture of jewelry, plate, and 
coin. It is alloyed with silver for the purpose of reducing its 
melting point. Copper and zinc, or copper, silver, and zinc may 
be used in this way. (Seepage 130 for formulae for gold alloys.) 

The term " carat" as applied to gold signifies 1/24 part and 
is used as a measure of purity of an alloy, 22 carat gold being 
22/24 pure gold. Twenty carat gold is 20/24 pure, etc. The 



METALS OF GROUP II. 



35 




Fig. 4. 



amount of gold in a given alloy may be determined approxi- 
mately by use of a device shown in Fig. 4, much used by 
jewelers, consisting of a series of stand- 
ard alloys and a piece of stone upon 
which the test is made. The tips are 
standard alloys. Parallel markings are 
made on the stone with the alloy in 
question and with the tip supposed to 
correspond to it; then the addition of a 
drop of strong nitric acid to the marks 
and a careful comparison of their ap- 
pearance will show if the two are of the 
same composition. 

If the composition of an alloy is 
known, the value in carats may be 
determined by the following: 

Rule to determine the carat of a given alloy: Multiply 24 
by the weight of gold used and divide result by total weight 
of alloy. For instance, if an alloy is made containing 9 parts 
of gold and 3 of another metal, the total weight will be 12 and 
the calculations 24 X 9 -5- 12 = 18. The alloy is an 18-carat 
gold. 

Gold may be raised to a higher carat by the following rule: 
Multiply weight of alloy used by difference between its carat 
and that of the metal to be added. Then divide product by the 
difference between the carat of the metal added and that of the 
required alloy. The figure thus obtained represents the total 
weight of required alloy. Subtract from this weight of material 
taken and difference in weight of pure or alloyed gold to be 
added. (From Hall's Dental Chemistry.) 

To reduce gold to a required carat Essig takes the following 
rule from Richardson's Mechanical Dentistry: "Multiply the 
weight of gold used by 24 and divide the product by the required 
carat. The quotient is the weight of the mass when reduced, 



36 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

from which subtract the weight of the gold used, and the re- 
mainder is the weight of the alloy to be added." 

Analytical Reactions. — Gold is insoluble in simple acids, 
but may be dissolved in nitrohydrochloric acid (aqua regia) with 
formation of auric chlorid. Gold also unites easily with Br or 
I, forming AuBr 3 or Aul 3 . A one-half per cent solution of AuCl 3 
may be used in the following tests : 

H 2 S with AuCl 3 gives dark brown Au 2 S 3 (auric sulphid), 
soluble in yellow ammonium sulphid. 

Gold is reduced to the metallic state by' many of the other 
metals, as Pb, Cu, Ag, Sn, Al, Sb, Fe, Mg, Zn, and Hg; also 
by ferrous sulphate, stannous chlorid, and oxalic acid. 

Add a freshly prepared solution of ferrous sulphate to a 
little acid solution of AuCl 3 . Gold is precipitated as follows: 
AuCl 3 + 3 FeS0 4 = Au + Fe 2 (S0 4 ) 3 + FeCl 3 . 

Stannous chlorid precipitates from gold solution the " purple 
of Cassius, " consisting of a mixture of gold and oxid of tin in 
colloidal forms. 

Gold is only slowly precipitated by oxalic acid; but, as Pt 
is not precipitated at all by this reagent, it is possible to separ- 
ate Au and Pt in solution, as chlorids, by this means. 

KI will give a dark-green precipitate of Aul 2 provided the 
KI is in excess; if the gold is in excess, the precipitate is apt 
to be the yellow Aul (aurous iodid). In the presence of a con- 
siderable excess of KI the Aul 3 is kept in solution as the potassio- 
auric iodid, KIAuI 3 . The reduction of this double salt by 
sodium thiosulphate is made the basis of the method to determ- 
ine the quantity of Au in a given alloy, as described in the 
chapter on Volumetric Analysis. 

Platinum, Pt. 

Atomic weight 194.8. Melting-point 2000 C. Platinum 
solubilities are similar to gold; aqua regia forms the chlorid 
PtCl 4 . 



METALS OF GROUP II. 37 

Alloys. — Platinum alloys quite easily with other metals, 
particularly lead; and platinum utensils may be destroyed by 
heating in contact with the compounds of metals easily reduced. 
Sulphur and phosphorus also attack platinum. 

Platinum 90% and iridium 10% give an alloy harder, more 
brittle, and more resistant to chemical action than pure platinum. 

11 Platinum Color," for coloring enamel, is made, according 
to Mitchell's Dental Chemistry, by precipitating platinum 
from a solution of PtCl 4 by boiling with KOH and grape sugar; 
then, grinding this finely divided platinum with feldspar in the 
proportion of 1 part Pt to 16 parts feldspar. 

Analytical Reactions. — PtCl 4 + H 2 S gives a precipitate of 
sulphid of platinum almost black, soluble in yellow ammonium 
sulphid. 

Platinum solution with NH 4 C1 precipitates yellow ammo- 
nium platinic chlorid, (NH 4 ) 2 PtCl6, crystalline. Potassium 
chlorid also gives a yellow crystalline precipitate of K 2 PtCl6, 
isomorphous with the ammonium compound. (Plate III, 
Figs. 1 and 3.) These reactions may be made quantitative by 
using neutral, fairly concentrated solutions and adding an equal 
volume of alcohol. 

Both of these double salts are soluble in excess of alkali, and 
reprecipitated by HO. 

Stannous chlorid reduces PtCl 4 to PtCl 2 but forms no pre- 
cipitate. Metallic Zn will precipitate platinum as a fine black 
powder or spongy mass. 

Analysis of Group II. 

Separation of parts (a) and (b) . 

A portion of the clear filtrate, from Group I, containing a 
slight excess of HC1 is tested for metals of Group II by the 
addition of H 2 S water.* 

* A preliminary test is made on a part of the solution because in the absence 
of Group II, the analysis of Group III can be made more easily without the pres- 
ence of H2S. 



3& SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

If a precipitate is obtained, warm the whole of the solution 
and pass in H 2 S gas for from three to five minutes, which pre- 
cipitates all metals of the group as sulphids. Filter. 

Break point of filter-paper with glass rod and wash Group II 
into beaker with warm (NH 4 ) 2 S; digest hot for a few minutes. 

Filter and wash the precipitate till wash-water shows only 
traces of CI. Throw away all wash-water except the first. 



Group II (a). Cu, Cd, Bi, Hg, and Pb. 




Group II (b). As, Sb, Sn, Au, and Pt. 



Analysis of Group II (a). 
Dissolve the precipitate off the paper with hot dilute HNOj 



Hg, if present, will remain on paper, black. 



Filtrate contains nitrates of Pb, Cu, Cd, and Bi. 



Test black residue on paper for Hg" by dissolving in aqua 
regia and precipitating with SnCl2. For reaction between SnCl 2 
and HgCl2 see page 24. Aqua regia may be made by mixing 
two or three parts of HC1 with one part of HN0 3 . Free CI is 
liberated which dissolves the HgS as HgCl 2 . 

3 HC1 + HNO3 = NOC1 + 2 H 2 + Cl 2 . 

If lead is present in Group I, the nitrate above will con- 
tain traces which must be separated by adding a few drops of 
H2SO4 and allowing to stand at least fifteen minutes. Filter. 




METALS OF GROUP II. 



39 




PbSCh remains on paper. 



Filtrate contains Cu, Cd, Bi. 



To the filtrate add NH4OH till alka- 
line; Bi separates as Bi(OH) 3 , white. Filter. 




Bi(OH) 3 . 



Cu and Cd. 



Divide the filtrate (Cu and Cd) into two parts. A blue color 
indicates presence of Cu. With one part test for Cu by making 
it acid with acetic acid and adding K 4 FeCy 6 , which will give 
a brown precipitate of Cu 2 FeCy6. With the other part test 
for Cd by adding solid KCN very carefully till all blue color 
has disappeared; then a little H 2 S water will give a yellow pre- 
cipitate of CdS if cadmium is present. 

Analysis of Group II (b). 

To the ammonium sulphid add HC1 till acid. A very fine 
white precipitate may be sulphur only. 

Filter and wash. Throw away wash-water. Pierce filter 
and wash sulphids into large test-tube or small beaker. Add 
10 c.c. of (NH 4 )2C0 3 and heat for a few minutes. Filter. 



Sb, Sn, Au, Pt sulphids. 




Arsenic sulphid. 




40 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Add HC1 and Zn and make Gutzeit's test (page 28) and if 
necessary Fleitmann's (page 29) or Marsh's (page 32). 

Dry this precipitate upon paper and place paper and pre- 
cipitate in a porcelain evaporator, add concentrated HC1 and 
heat. (This must be done under the hood.) Dilute and filter, 
when Au and Pt will remain undissolved. 



Au and Pt. 



Sb and Sn. 



To the Sb and Sn solution add a little Zn and a piece of 
platinum-foil. The antimony and tin will both be reduced to 
the metallic state, the Sb being deposited on the Pt as a brown 
or black coating. Presence of Sb may be confirmed by remov- 
ing the Pt, washing carefully, treating with (NH 4 ) 2 S, and dry- 
ing, when the coating will become Sb 2 S 3 , orange-red. 

To the solution to be tested for Sn add HC1 enough to dis- 
solve all the Zn which has been added, filter, and test filtrate with 
HgCl 2 (page 3 8). 

Dissolve the insoluble residue of Au and Pt (the residue 
will be dark-colored if either of these metals are present) in 
aqua regia and divide solution into two parts. 

Test one part for gold with solution of FeS0 4 , or a mixture 
of SnCl 2 and SnCl 4 (page 36). 

Test the other part for Pt by adding NH 4 C1, allow to stand 
overnight adding a little alcohol, and precipitate of ammonium 
platinic chlorid will be obtained, yellow and crystalline (see 
Plate 3, Fig. 1). 



METALS OF GROUP II. 4 1 

QUESTIONS ON GROUP II. 

Why is it necessary to wash the precipitate of Group II 
practically free from CI before dissolving in warm HN0 3 ? 

How does the Hg found in Group II differ from the Hg in 
Group I? 

How does the Pb found in Group II differ from the Pb in 
Group I? 

Before making the final test for Sn, why is it necessary to 
dissolve all the Zn which has been added ? 

In precipitating Group II why should the solution be made 
acid with HC1 before adding H 2 S ? 

Why is it better to use H 2 S gas rather than H 2 S water in 
precipitating metals of Group II ? 

Before testing for Cd why add KCN to decolorize the copper 
solution ? 

Laboratory Exercise IV. 
Analytical reactions of the copper group {pages 22-26). 

Laboratory Exercise V. 
Analysis of copper and the silver groups. 

Laboratory Exercise VI. 
Special tests for arsenic (pages 28-31). 

Laboratory Exercise VII. 
Preliminary reactions of the arsenic group (pages 32-34) and 
analysis of unknown solutions. 

Laboratory Exercise VIII. 
Unknown solutions. 



42 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Laboratory Exercises IX. 
Experiments with metals of Groups I and II . 

Exp. 10. Precipitate a little silver chlorid according to the 
following: 

AgN0 3 + NaCl = AgCl + NaN0 3 . 

Filter and allow the precipitate to become nearly dry. Mix a 
little of the precipitate with powdered charcoal, and heat be- 
fore the blowpipe until a globule of metallic silver is obtained. 

Exp. n. Mix intimately a small quantity of litharge and 
powdered charcoal. Heat in a blowpipe name and obtain a 
particle of metallic lead. 

Exp. 12. In a solution of lead (acetate or nitrate) suspend 
a strip of zinc. Set aside for several hours and note the sepa- 
ration of metallic lead. Write the reaction. 

Exp. 13. Put a small quantity of cinnabar (HgS) into a 
small, hard glass tube open at both ends. Hold the tube, slightly 
inclined, in a strong heat of the Bunsen name; then examine the 
sublimate under the microscope. What becomes of the sulphur? 

Exp. 14. Hold a strip of iron or steel (knife blade) for a 
few seconds in a solution of copper sulphate. Does the strip of 
iron dissolve ? If so, in what combination ? 

Exp. 15. In an open, hard glass tube, heat strongly a mix- 
ture of charcoal and copper oxid. Explain the change of color. 

Exp. 16. To a very small piece of copper foil in a test-tube, 
add a little ammonium chlorid solution and allow to stand. 



CHAPTER V. 
METALS OF GROUP III. 

Iron, Fe (Ferrum). 

The Metal. — Atomic weight 55.9. 

Melting-point 1275 C. Iron occurs widely distributed in 
nature combined with oxygen as Fe20 3 or Fe 3 04, with sulphur 
as FeS 2 , and with carbon as FeC0 3 . 

The reduction of iron from its ores is typical of one of -the 
four general methods, that is, reduction by carbon. This is 
carried out in the blast furnaces, which are so constructed that 
a supply of coal, iron ore, and fusible slag, introduced at the 
top of the furnace, are dissolved and hold impurities, while the 
purified molten metal is withdrawn from the bottom. This 
melted iron, cast in molds as it comes from the furnace, con- 
stitutes our cast iron, is brittle, and contains a considerable 
proportion of carbon and other impurities. 

Wrought iron is produced by working melted iron in specially 
constructed furnaces so that the greater part of the impurities 
are removed. By the addition, to very pure iron after such 
treatment, of carbon, manganese, etc., steel is produced. 

Reduced iron or "iron by hydrogen" is prepared by the re- 
duction of the heated oxid or hydroxid in a stream of hydrogen 
gas. 

Compounds. — Iron forms two classes of salts, ferrous, 
represented by ferrous sulphate, FeS0 4 ; and ferric, represented 
by ferric sulphate, Fe 2 (S0 4 ) 3 , or ferric chlorid, FeCl 3 . 

Ferric sulphate, also known as Monsel's salt, is used as a 
styptic. 

43 



44 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Ferric chlorid, FeCl 3 or Fe 2 Cl6, is made by dissolving iron 
in hydrochloric acid, oxidizing the ferrous chlorid with nitric 
acid, and then driving off the nitric acid by evaporation. The 
resulting solution, however, contains traces of free nitric and 
considerable free hydrochloric acid. In the tincture of chlorid 
of iron these acids react with the alcohol forming various ethers, 
to which the peculiarities of the tincture may be due. 

Copperas and green vitriol are commercial names for crys- 
tallized ferrous sulphate. FeS0 4 7H 2 is used as a disinfectant 
and, to a slight extent, in medicine as an astringent. 

Ferrous carbonate, (FeC0 3 )#(Fe(OH) 2 )y, prepared by double 
decomposition between FeSCU and potassium or sodium car- 
bonate, is a medicinal preparation quite largely used as "Blaud's 
pills." 

Analytical Reactions. — A solution for demonstrating the 
reactions of ferrous salts is best made by saturating cold dilute 
sulphuric acid with clean iron wire. A 3 to 5 per cent solution 
of fresh crystals of ferrous ammonium sulphate may be used. 
The ordinary ferrous sulphate or ''copperas" is almost sure to 
contain some ferric salt. Use a 2 to 3 per cent solution of ferric 
chlorid and make the following tests, comparing the deport- 
ment of the ferrous and ferric solutions with each reagent. 
Write the reactions. 

H 2 S with pure ferrous salts gives no reaction; with ferric 
salts the iron is reduced to the ferrous combination, but gives 
no precipitate except sulphur. 

(NH 4 ) 2 S gives with ferrous iron a black precipitate of FeS; 
with ferric salts it gives a precipitate containing FeS and S. 

NH4OH precipitates Fe" as ferrous hydroxid, Fe(OH) 2 ; 
white if perfectly pure, but usually a dirty green from admix- 
ture of ferric compounds. The presence of NH 4 C1 prevents 
a complete precipitation as Fe(OH) 2 . 

With ferric salts, NH 4 OH completely precipitates the iron 
as brick-red ferric hydroxid, Fe(OH) 3 . 



METALS OF GROUP III. 45 

K 4 FeCy 6 gives with ferrous salts a bluish-white precipitate 
of potassium ferrous ferrocyanid, K 2 FeFeCy6. 

With a solution of ferric salts the deep Prussian blue, ferric 
ferrocyanid, Fe 4 (FeCy 6 )3, is thrown out. 

With potassium ferricyanid, ferrous salts give a dark-blue 
precipitate of ferrous ferricyanid, Fe3(FeCy 6 ) 2 . With ferric 
salts no precipitation occurs, but the color may change to green 
or brown. 

KCyS or NH 4 CyS gives no reaction with pure ferrous salts, 
but with ferric salts a deep red solution of ferric thiocyanate, 
Fe(CyS) 3 , is produced. This red color is destroyed by addi- 
tion of HgCl2, not affected by HC1, and may be extracted from 
the aqueous solution by shaking with ether in which the 
Fe (CyS) 3 is soluble. 

Aluminum, Al. 

Atomic weight 27.1. Melting-point 700 C. Aluminum 
as a constituent of clay, feldspar, mica, etc., constitutes a con- 
siderable part of the earth's crust. 

Alloys. — Aluminum alloys are not difficult to produce, but 
few are of practical value. The pure metal is used in making 
plates. The following may be noted. 

Aluminum alloys for bridge work. Dr. Richards, Paris, 
Dental Cosmos, March, 191 2, page 378, 

(1) (2) 

Copper 5.5 Tin 7 

Tin 2.0 Zinc 10 

Aluminum 92.5 Aluminum 83 

Number two is more elastic than number one and either 
makes a better appearance than pure aluminum. 

Compounds. — The most important soluble salts of Al are 
ammonia alum, NH 4 A1(S0 4 ) 2 12 H 2 0, potash alum, KA1(S0 4 ) 2 
12 H 2 0, and aluminum sulphate, A1 2 (S0 4 ) 3 . 

The term alum is applied to any salt of definite crystalline 



46 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

form containing one molecule of a univalent sulphate, such as 
K 2 S0 4 or Na 2 S0 4 , combined with one molecule of a trivalent 
sulphate, A1 2 (S0 4 ) 3 , Fe 2 (S0 4 ) 3 or Cr 2 (S0 4 ) 3 , and crystallized with 
twenty-four molecules of water. The formula of alum, as given 
above, comprises just one half of this combination. Alum need 
not contain any aluminium whatever so long as it conforms to the 
foregoing requirements, e.g., chrome alum may be NH 4 Cr(S0 4 ) 2 
12 H 2 and ferric alum is usually NH 4 Fe(S0 4 ) 2 12 H 2 0. 

Analytical Reactions. — Use a 5% solution of either of these 
for the following tests : 

A1 2 (S0 4 ) 3 with (NH 4 ) 2 S and H 2 gives a white precipitate 
of Al(OH) 3 . Write the reaction. 

Al(OH) 8 is likewise produced by NH 4 OH, Na 2 C0 3 , or NaOH; 
the precipitate is soluble in excess of fixed alkali hydroxids with 
formation of aluminates: 

Al(OH) 3 + KOH = KA10 2 + 2 H 2 0. 

The alkaline aluminates may also be formed by fusion with 
Na 2 C0 3 and KN0 3 and then may be dissolved in hot water. 

From the solution of KA10 2 the Al may be precipitated as 
Al(OH) 3 by excess of NH 4 C1 (difference from Zn, page 55). 

The presence of organic acids, tartaric, oxalic, etc., inter- 
feres with the precipitation of aluminium hydroxid and may 
entirely prevent it. The presence of ammonium chlorid favors 

its precipitation. 

Chromium, Cr. 

Atomic weight 52.1. Occurs as chrome iron ore or chromite, 

FeOCr 2 3 . Chromium forms two oxids, one basic in character, 

Cr 2 3 , which forms the basis of chromic salts, as Cr 2 (S0 4 ) 3 , 

Cr 2 Cl 6 (CrCl 3 ),* etc.; the other, Cr0 3 , is an acid anhydrid, 

crystallizes as dark-red needles, and gives rise to two series of 

salts: neutral chromates, such as K 2 Cr0 4 , and acid chromates 

or dichromates, K 2 Cr 2 7 . 

* There is a series of chromous salts, CrCl 2 , Cr(OH) 2 , etc., corresponding to 
a chromous oxid, CrO, but the oxid itself is not known 



METALS OF GROUP III. 47 

The soluble chromic salts most easily obtained are chrome 
alum, KCr(S0 4 ) 2 , chromic sulphate, Cr 2 (S0 4 )3, and chromic 
chlorid, CrCl 3 . With a 5% solution of either of these the fol- 
lowing may be demonstrated: 

Cr 2 (SO) 3 with (NH 4 ) 2 S gives greenish precipitate of Cr(OH) 3 . 

Similarly to Al, the chromium hydroxid is precipitated by 
the alkaline carbonates and the alkaline sulphids as well as by 
the hydroxids; and then by boiling the Cr(OH) 3 with NaOH 
or KOH, or by fusing with Na 2 C0 3 and KN0 3 , chromates of the 
alkalis are produced. 

The solid dichromate K 2 Cr 2 7 with strong H 2 S0 4 gives, in 
the presence of chlorids, the reddish-brown gas Cr0 2 Cl 2 (chloro- 
chromic anhydrid or chromium dioxy chlorid) used as a test 
for chlorids (page 90) . 

Analysis of Group III. 

(Fe, Al, Cr. Phosphates and oxalates being absent.) 

The nitrate from Group II must be freed from H 2 S by boil- 
ing with a few drops of HN0 3 in a porcelain dish till a drop 
removed by a glass rod does not blacken filter-paper wet with a 
solution of lead acetate. This treatment also serves to oxidize 
the iron (reduced by H 2 S) to ferric salt and at the same time 
concentrates the solution. To the clear solution thus obtained 
add 10 c.c. of NH 4 C1 solution, then NH 4 OH till alkaline, when 
the metals of this group will separate out as hydroxids: Fe(OH) 3 
brick-red, Al(OH) 3 white, Cr(OH) 3 bluish-green. Filter, wash 
carefully, and dry precipitates, removing paper from funnel. 



Group III. 

Groups IV, V, and VI. 




48 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




Scrape dried precipitate from paper in 
a crucible and cover well with a mixture of 
dry Na 2 C0 3 and KN0 3 and fuse, keeping 
fusion liquid for at least three minutes. 
Cool. Boil the fused mass with H 2 0. 
Filter. 



Al and Cr. 



Iron will remain on the paper; Al and Cr will be in solution 
as alkaline alumina te and chr ornate. 

Divide filtrate (Al and Cr) into two parts. Test one por- 
tion for Al, by acidifying with HC1, adding (NH 4 ) 2 C0 3 till 
alkaline, and boiling, when Al will separate as a white floccu- 
lent precipitate of Al 2 (OH) 6 . 

Test second portion of filtrate for Cr by acidifying strongly 
with acetic acid, boiling to expel C0 2 , and adding a few drops of 
a solution of lead acetate. A yellow precipitate (PbCrOJ in- 
dicates Cr. 

Wash the precipitate remaining on the paper (Fe) and dis- 
solve in dilute HC1. Divide resulting solution (FeCl 3 ) into 
two parts and confirm presence of Fe by testing one with K^FeCye 
(blue precipitate) and the other with KCyS (red solution) . 

If iron is found, determine in original substance whether 
ferrous or ferric, by use of tests described on pages 44 and 45. 

QUESTIONS ON GROUP III. 

Why boil off H 2 S before precipitating the group with NH 4 OH ? 
WhyaddHNOs? 



METALS OF GROUP III. 49 

Of what use is the nitrate of potash (KN0 3 ) in the fusion 
of the hydroxids of Al and Cr ? 

In making the final test for Cr why is it necessary to add 
acetic acid, and why boil off the C0 2 ? 

Why must HC1 be added before making the final test for 
Alwith (NH 4 ) 2 C0 3 ? 



Laboratory Exercise X. 

Iron, Aluminum, and Chromium. 

Exp. 17. (a) To 5 c.c. of dilute alum solution containing a 
little NH4CI, add NH 4 OH solution and heat. 

Note. — NH4CI aids in the complete separation of the Al 2 (OH) 6 . 

Write reaction. Will the precipitate dissolve in an excess of 
the reagent? 

(b) Repeat, using a chromium solution in place of the alum. 
Exp. 18. Dissolve a few crystals of FeS0 4 in water. Filter, 
if necessary, and to a portion of the clear solution add a little 
ammonia water. To another portion add a few drops of HN0 3 
and boil for two or three minutes. Carefully add ammonia 
water till a permanent precipitate is obtained. 

To a solution of ferric alum add a little ammonia. What 
change is produced by the HNO3 in the second part of the 
experiment. 

FeS0 4 + NH4OH = ? 
3 H2SO4 + 6 FeS0 4 + 2 HNO3 = ? 
Fe 2 (S0 4 ) 3 + NH4OH = ? 

Note. — The addition of sulphuric acid is not necessary to the oxidation by 
HNO3. It simplifies the reaction, as otherwise more or less ferric nitrate is formed. 

Exp. 19. Make a little fresh solution of potassium ferricy- 
anide, also a solution of ferrous sulphate, to which add a little 
H2SO4 and a piece of iron wire. After hydrogen ceases to be 



50 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

evolved make the following tests, completing the reaction in 
each case: 

FeS0 4 + K 3 FeCy 6 = ? Fe 2 Cl6 + K 3 FeCy 6 = ? 

FeS0 4 + K 4 FeCy 6 = ? Fe 2 Cl6 + K 4 FeCy 6 = ? 

FeS0 4 + KCyS = ? Fe 2 Cl6 + KCyS = ? 

Exp. 20. To a solution of chrome alum add a little NH 4 OH. 
Filter, wash the precipitate once or twice and allow to dry. 

Cr 2 (S0 4 ) 3 + NH 4 OH = ? 

Exp. 21. To the dried precipitate obtained in Exp. 20 add 
a little dry sodium carbonate and potassium nitrate. Mix 
thoroughly, transfer to a porcelain crucible and heat strongly 
for several minutes, cool and note the color of the fused mass. 
Dissolve in water, acidify with acetic acid, and divide the solu- 
tion into two parts; to the first add a few drops of a solution 
of Pb(N0 3 ) 2 or Pb(C 2 H 3 2 ) 2 , and to the second a few drops of 
BaCl 2 . 

Exp. 22. To separate solutions of aluminum, iron, and 
chromium salts, add (NH 4 ) 2 S. Iron alone forms a sulphid; the 
other two give precipitates of hydroxids. Write the reactions. 

Laboratory Exercises XI and XII. 

Analyses of unknown solutions containing metals of Groups I y 
IL and III. 



CHAPTER VI. 
METALS OF GROUP "IV. 

Cobalt, Co. 

The Metal. — Atomic weight 59.0. Cobalt occurs in nature 
as an arsenide C0AS2, smaltite; also CoAsS, cobaltite. These 
ores are poisonous and have in times past caused the miners so 
much trouble that the name cobalt was applied to them, the 
word meaning, " A demon or mountain sprite. " Metallic arsenic 
has also been called cobalt. These facts are probably responsi- 
ble for a reputation which is attached to the pure oxid of cobalt. 

Analytical Reactions. — Use a 2% solution of nitrate. 
Crystalline salts of Co are usually of pink color; anhydrous 
salts are blue. 

Co (NO 3) 2 with (NH 4 ) 2S gives precipitate of CoS , black. Test 
solubility of this precipitate in HC1. 

Make a borax bead by fusing a little borax on the looped end 
of a clean platinum wire. When a bead of clear "borax glass" 
has been obtained, dip it in a little of the CoS just formed, and 
fuse again. The color of the bead when cold is a deep blue. 

Note. — Be sure and make the fusion complete; the use of an insufficient 
amount of heat will account for much of the trouble experienced by students in 
obtaining satisfactory bead tests. 

Co(N0 3 ) 2 with KN0 2 forms a double nitrite, Co(N0 2 ) 2 
2 KN0 2 , soluble in water; but if sufficient acetic acid is added 
to produce a strong acid reaction, the solution heated, and then 
allowed to stand overnight, the cobalt is completely precipitated 
as another double salt, Co(N0 2 ) 3 ,3KN0 2 , yellow and crystalline. 

si 



52 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Nickel, Ni. 

Atomic weight 58.7. Occurs associated with Co, some- 
times with Fe as sulphid. 

The metal is white, hard, and has a high melting-point. It 
is soluble in dilute mineral acids, mdst easily in nitric. It is 
the least malleable of the common metals. 

Alloys. — The principal alloys are German silver, containing 
copper, nickel, and zinc, and an alloy of 25% nickel and 75% 
copper, used by the United States Government in making five- 
cent pieces. 

Nickel is largely used for plating steel and copper. 

Analytical Reactions. — Use a 2 % solution of the sulphate 
or nitrate. NiS0 4 with (NH 4 ) 2 S gives NiS, black. Test solu- 
bility in HC1. 

The borax-bead test applied to NiS or other nickel salt gives 
a bead yellowish brown when cold, but the color is easily masked 
by other metals. 

Ni salts with KN0 2 give the soluble double nitrite of similar 
composition to the Co salt, Ni(N0 2 )2, 2 KN0 2 . The nickel 
salt, unlike the cobalt, is not easily decomposed, and is not 
precipitated by heating with acetic acid. Advantage is taken 
of this fact in effecting the separation of cobalt from nickel 
(page 56). 

Manganese, Mn. 

Atomic weight 55.0. Occurs chiefly as the dioxid, Mn0 2 , 
pyrolusite. 

Compounds. — The black oxid, Mn0 2 , is commercially im- 
portant in the production of chlorin. By Weldon's process, 
the chlorin is obtained from HC1, the pyrolusite acting as an 
oxidizing agent. 

The oxidization of Mn0 2 in the presence of KOH results in 
the formation of potassium permanganate, KMn04- This salt 
is a valuable disinfectant and is largely used. Its decomposition 



METALS OF GROUP IV. 53 

furnishes 5 atoms of available oxygen from every double mole- 
cule (K 2 Mn 2 8 ). 

Condy's fluid, a commercial disinfectant, is a solution of 
KMn0 4 . 

Manganese salts are usually flesh-colored. 

Analytical Reactions. — A 3% solution of the sulphate may 
be used in the following tests : 

MnS0 4 with (NH 4 ) 2 S gives flesh-colored precipitate of MnS. 
Test solubility in HCL With a little of the precipitated MnS 
make a red-lead test for Mn as follows : 

Place in a test-tube a little red lead (Pb 3 4 ). Add three or 
four cubic centimeters of a solution of nitric acid (about one 
part of concentrated HN0 3 and one of H 2 0) , and boil well. Add, 
by means of a glass rod, a little of the washed MnS to the mix- 
ture in the tube and boil again. Now dilute with water till the 
tube is about three-quarters full, and allow to stand till liquid 
is clear. If Mn is present, the supernatant fluid will be a pink 
to red color due to the formation of permanganic acid, 
HMn0 4 . 

Note. — HC1 or chlorids, even in small quantities, interfere with the reaction; 
hence it is recommended to make the test on the sulphid. Reducing agents must 
likewise be absent. When these precautions are observed the test is a very simple 
and an extremely delicate one. 

MnS0 4 with NaOH gives flesh-colored Mn(OH) 2 insoluble 
in excess of reagent (separation from Zn). 

Upon fusion with a mixture of KNO3 and Na 2 C0 3 , man- 
ganese salts produce green manganates, as Na 2 Mn0 4 . 

Zinc, Zn. 

The Metal. — Atomic weight 65.4. Melting-point 420 C. 
(burns). Occurs chiefly as the carbonate, ZnC0 3 , calamine. A 
native carbonate of zinc is also known as smithsonite. The 
sulphid, ZnS (zinc blende), and the silicate are also natural sources 
of the metal. 



54 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

These ores of zinc, whether sulphate or carbonate, upon 
roasting in air are converted into oxide, and the oxide is easily 
reduced by carbon to metallic zinc. The metal is bluish white 
in color, melts at 420 C; is brittle at ordinary temperatures, 
but malleable and ductile at 140 to 150 C. At 200 C, how- 
ever, it again becomes brittle and fuses as above stated at 420 C. 
At 950 zinc boils and may be distilled; in air it ultimately 
burns to a white sulphate. 

Alloy. — Zinc is of considerable importance' from a dental 
standpoint, the metal itself being used in the manufacture of 
counter- dies and solders; and, according to Mitchells' Dental 
Chemistry, it may be advantageously used in the proportion of 
1 to 1.5% in silver-tin amalgam alloys. "It tends to control 
shrinkage, imparts a 'buttery' plasticity to the amalgam, adds 
to the whiteness of the filling and assists in the maintaining of its 
color." 

Compounds. — The oxide of zinc combines with phosphoric 
acid and is peculiarly adapted to the preparation of dental 
e cements. Zinc salts with alkaline carbonates precipitate a 
white basic carbonate, Zn 5 (OH) 6 (C03) 2 , which is used as a pig- 
ment in the preparation of paint and also as a source of pure 
oxide of zinc. 

The sulphate, ZnS0 4 , also known as white vitriol, is per- 
haps the most common salt. The chlorid is a constituent 
of many commercial liquid disinfectants and antiseptics. The 
nitrate also is easily obtained. 

A 2 or 3 per cent solution of any of these soluble salts may be 
used in the following tests : 

Analytical Reactions. — ZnS0 4 with (NH^S gives a white 
precipitate of ZnS. 

Sulphid of zinc is the only white sulphid formed in the course 
of analysis of ordinary solutions, but the following white pre- 
cipitates are formed: Sulphid of manganese is flesh-colored or 
dirty white. Aluminum hydroxid resembles sulphid of zinc in 



METALS OF GROUP IV. 55 

appearance and is precipitated by (NH 4 ) 2 S. Yellow (NH 4 ) 2 S 
added to an acid solution will precipitate sulphur, white, very 
fine and difficult to filter out. 

ZnS0 4 with NaOH (or KOH) gives a white gelatinous pre- 
cipitate of zinc hydrate, Zn(OH) 2 , soluble in excess of the reagent 
as Na 2 Zn0 2 (sodium zincate) . 

Note. — Colorless gelatinous precipitates in slight amounts may escape de- 
tection, as it sometimes takes careful observation to see them, especially if the 
laboratory light happens to be poor. 

Na 2 Zn0 2 with H 2 S or (NH 4 ) 2 S gives precipitate of ZnS. 

From solution of Na 2 Zn0 2 the Zn may be precipitated as 
Zn(OH) 2 by addition of NH4CI, but further addition of the 
NH 4 C1 redissolves the precipitate (distinction from Al, page 46). 

ZnS0 4 with K 4 FeCy 6 gives white precipitate of zinc ferro- 
cyanid (Zn 2 FeCy 6 ), insoluble in NH 4 OH. 

Note. — The ferrocyanid and the sulphid are the only two zinc salts not soluble 
in NH4OH. (Prescott and Johnson, page 179.) 

Soluble zinc salts, with oxalic acid or oxalates, give a pre- 
cipitate of zinc oxalate sufficiently insoluble in alcohol and 
water to make it available for use in the quantitative separation 
of zinc from dental alloys. The crystals are of characteristic 
form, which may be recognized under a microscope (Plate II, 
Fig. 6, page 162). 

y 
/ 

Analysis of Group IV. 

(Co, Ni, Mn, Zn.) 

(In the presence of phosphates, oxalates, borates, etc., 
examine this group by the scheme given on page 80). 

To the clear filtrate from Group III add (NH 4 ) 2 S. A pre- 
cipitate may be NiS, CoS, MnS, and ZnS. Wash the precipitate 
and treat with cold dilute HC1, which will dissolve MnS and ZnS 
only. 



56 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




CoS and NiS, black. 



MnCl 2 and ZnCl 2 in solution. 



Make a borax-bead test (page 51) of the precipitates. If 
a clear red-brown bead is obtained, Ni alone is present. If 
the bead is blue, Co is present, Ni may or may not be. 

Separation of Cobalt and Nickel. 

If Co is present, dissolve the black precipitate off the paper 
with aqua regia, evaporate in porcelain capsule practically to 
dryness, dissolve in H 2 0, add excess of acetic acid and potassium 
nitrite (KN0 2 ). Allow to stand over night, when Co will 
separate out as a yellow crystalline precipitate (page 51). 

Filter and test filtrate for Ni with NaOH, which gives a 
pale-green precipitate of Ni(OH) 2 insoluble in excess of the 
precipitant. 

Separation of Manganese and Zinc. 

Boil the HC1 solution of Zn and Mn to expel the H 2 S, then 
add a decided excess of KOH or NaOH and allow to stand ten 
minutes without heating. Mn will separate out as Mn(OH) 2 , 
while Zn will remain in solution as K 2 Zn0 2 . 




Mn(OH) 2 . 



K 2 Zn0 2 . 



METALS OF GROUP IV. 57 

Test precipitate by the red-lead test for Mn, page 53. Test 
filtrate for Zn by adding H 2 S or a few drops of (NH 4 ) 2 S, which 
will precipitate ZnS, white. 

QUESTIONS ON GROUP IV. 

Why dissolve the MnS and ZnS in cold and dilute HC1 ? 

Why is it necessary to separate all the Mn before testing 
for Zn ? 

If traces of Co or Ni are dissolved by the HO, how does it 
affect the final test for Zn ? 

In this analysis (in absence of phosphates, etc.) what im- 
portant difference between the behavior of salts of Zn and Al? 

Why is it necessary to allow time for complete precipitation 
of CowithKN0 2 ? 

Why expel H 2 S before separating Mn? 

Where does this H 2 S come from? 

Laboratory Exercise XIII. 
Cobalt, Manganese, Nickel and Zinc. 

Exp. 23. Add to solutions of Co(N0 3 ) 2 , MnS0 4 , Ni(N0 3 ) 2 
and ZnS0 4 a few drops of (NH 4 ) 2 S solution. 

Note color of precipitate and write reaction in each case. 

Exp. 24. On four separate filter papers collect the several 
precipitates formed in Exp. 23. Wash once with H 2 and make 
a borax-bead test with each precipitate as shown in the labora- 
tory demonstration. To each precipitate add, on the paper, 
cold dilute HC1. 

Exp. 25. (a) To a solution of ZnS0 4 add a little NH 4 OH. 
Will the precipitate dissolve in excess of reagent ? 

(b) Repeat, adding NH 4 C1 before using the NH 4 OH. 

(c) Repeat (a) using NaOH in place of NH 4 OH. 

Exp. 26. Precipitate a little MnS, filter and wash. Make 
red-lead test as described on page 53. 



58 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Exp. 27. (a) To a solution of Co(N0 3 )2 in a test-tube, add 
a drop or two of dilute NH 4 OH. Now add an excess of NH 4 OH 
and note if any change occurs. 

(b) Repeat, using a solution of NiS0 4 . 

What are the precipitates formed ? 

Exp. 28. To a solution of zinc salt add a solution of Na 2 C0 3 . 
The precipitate is a basic carbonate of zinc. 

Balance the equation 

ZnS0 4 + Na 2 C0 3 + H 2 = Zn 5 (OH) 6 (C0 3 ) 2 + Na 2 S0 4 + C0 2 . 

Exp. 29. Shake in a test tube a little ZnO and water, filter 
and test filtrate for Zn as in Exp. 23. 

Repeat using ammonium chloride solution instead of the 
water. Inference. 

Laboratory Exercise XIV. 
Analytical reactions of metals of the zinc group. (Pages 51-56.) 

Laboratory Exercises XV and XVI. 
Unknown solutions. 



CHAPTER VII. 
METALS OF GROUP V. 

The Alkaline Earths Ba, Sr, Ca, Mg. 

The common alkaline earth metals present similarity of 
properties which ally them more closely than the metals of some 
of the previous analytical groups. None of the metals occur 
free in nature. The metals themselves are isolated with con- 
siderable difficulty, with the exception of magnesium, and they 
all decompose water with evolution of hydrogen, calcium, stron- 
tium and barium producing the decomposition at ordinary tem- 
peratures; magnesium, at high temperatures only. 

As a group they form insoluble carbonates, from which C0 2 
is easily driven off by heat, leaving the oxid of the metal. This 
oxid unites with water, forming feebly soluble hydroxids. 
The solutions of the hydroxids are alkaline to litmus, and are 
used, to a considerable extent in medicine, as antacids. 

There are two other metals belonging to this group. The 
first, glucinum, also called beryllium, has an atomic weight of 
9.1. Soluble salts of glucinum are precipitated by ammonium 
hydroxid as white and gelatinous Be(OH) 2 . The precipitate 
somewhat resembles aluminum hydroxid. Ammonium carbon- 
ate also precipitates the hydroxid which is easily soluble in excess 
of reagent. The solution, however, should not be boiled as pro- 
longed boiling will cause the glucinum hydroxid to reprecipitate. 

Beryllium oxid unites with phosphoric acid, forming a phos- 
phate similar in its properties to the basic phosphate of zinc, and 
its use is claimed by some manufacturers to be essential to the 
preparation of artificial enamels. (See page 124.) 

59 



60 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The second rare metal belonging to this group is radium; 
atomic weight 225. The metal itself has not as yet been iso- 
lated. Its compounds are obtained from uraninite or pitch- 
blende, a source of uranium. It is bivalent, and the chlorids, 
bromids, nitrates, and hydroxids have been studied. 

Radium compounds are luminous, and the active emanations 
emitted by them have been condensed at 150 below zero centi- 
grade, forming new substances, among which helium has been 
identified. The discovery of this fact is responsible for our new 
conception of the possible divisibility or disintegration of what 
were once considered indivisible atoms, the "smoke ring" mole- 
cule, and the possible transmutation of the elements. 

Barium, Ba. 

Compounds. — Barium, the next metal to radium in this 
group in point of atomic weight, which is 137.4, occurs chiefly 
as a sulphate BaS0 4 , heavy spar, and BaC0 3 , witherite. Barium 
oxid may be formed by heating the carbonate or nitrate to red 
heat. It absorbs oxygen from the air with formation of the 
binoxid Ba0 2 . This in turn is decomposed, oxygen being given 
off and BaO being reproduced. The barium oxid hence be- 
comes a source of oxygen of commercial importance. The cost 
of producing oxygen by this method is obviously small. 

The peroxid of barium is also of particular importance to the 
dentist, in that it is an important source of peroxid of hydrogen. 
This substance is considered more fully in a chapter on mouth 
washes and local anaesthetics. (See page 171.) 

Barium hydroxid, Ba0 2 H 2 , slightly soluble in water, absorbs 
C0 2 very rapidly and may be used as a test for this gas. The 
solution is known as "Baryta Water." 

Analytical Reactions. — Use a 2% solution of the chlorid 
for tests. 

BaCl 2 with (NH 4 ) 2 C0 3 gives white precipitate of barium 



METALS OF GROUP V. 6 1 

carbonate. Test solubility in acids. With soluble sulphates 
BaCl 2 produces BaS0 4 insoluble in HC1. (Test for sulphates.) 

BaClo with K 2 Cr 2 7 or K 2 Cr0 4 gives yellow precipitate of 
BaCr0 4 . Barium salts moistened with HC1 and held on a clean 
platinum wire give to the colorless flame of the Bunsen burner 
a green or yellowish-green color. 

Strontium, Sr. 

Atomic weight 87.6. Occurs as the carbonate, SrC0 3 , 
strontianite, also as the sulphate. 

Strontium salts are used commercially in the preparation of 
colored fires, strontium imparting a vivid red color to the flame. 
They are not used medically. Strontium oxalate crystallizes 
in practically the same forms and much more easily then cal- 
cium oxalate. 

Analytical Reactions. — Use a 3 to 4% solution of the nitrate 
or chlorid for tests. 

Sr(N0 3 ) 2 with (NH 4 ) 2 C0 3 gives white precipitate of SrC0 3 . 

Sr(N0 3 ) 2 with H 2 S0 4 or soluble sulphate gives white pre- 
cipitate of SrS0 4 , rather more soluble in water and more slowly 
formed than BaS0 4 . 

A saturated solution of SrS0 4 may be used to test for barium 
in presence of Sr salts. 

Sr(N0 3 ) 2 with K 2 Cr0 4 gives precipitate of SrCr0 4 , but with 
the acid chromate (dichromate) of potassium, K 2 Cr 2 7 , no 
precipitate is formed except in concentrated solutions. 

Sr(N0 3 ) 2 with oxalic acid gives a precipitate of strontium 
oxalate, SrC 2 4 , crystallizing in the so-called envelop form 
(Plate II, Fig. 3, page 162). Salts of Sr color the Bunsen flame 
crimson. 

Calcium, Ca. 

Atomic weight 40.1. Calcium is widely distributed and 
very abundant, limestone, chalk, marble, and calc-spar being 



62 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

natural carbonates; CaC0 3 , gypsum, and alabaster are sul- 
phates. 

Calcium phosphate occurs in the mineral apatite and is also 
a principal constituent of animal bones. 

Calcium sulphate is of particular interest, occurring as 
gypsum, CaS0 4 .2 H 2 0. Upon heating, the two molecules of 
water of crystallization may be driven off, leaving the anhydrous 
CaS0 4 , or plaster of Paris, so largely used in dental laboratories. 
When water is added to the anhydrous powder, it reunites in the 
proportions of the original crystallized salt and thereby occasions 
the ''setting " of the plaster. Essig states that if, in the prep- 
aration of plaster, the heat is allowed to exceed 127 C, its 
affinity for water is impaired or destroyed and this effect will 
not be produced.* 

As plaster sets, more or less expansion takes place, and, if 
spread upon glass, the mass usually rises slightly in the center, 
producing a plate which is somewhat concave on the under 
surface. This tendency to expansion varies with different 
grades of plaster, as may easily be shown by a method suggested 
by Dr. George H. Wilson in the Dental Cosmos for August, 
1905, page 940, which consists simply of filling small glass 
beakers with mixtures similarly prepared. Some samples were 
found to expand so slightly as not to injure the glass, others 
cracked, and some broke the beaker into fragments. 

The method of mixing also affects the amount of expan- 
sion. In a valuable article on "Experiments in Plaster of Paris 
to Test Expansions," by Dr. Stewart J. Spence, in Items of 
Interest, 1902, page 721, it is shown that "not only do different 
plasters expand in differing degrees, but the same plaster expands 
very differently according to the stirring given it before pouring," 
and that long stirring increases the heat developed, the rapidity 
of setting, and the amount of expansion, but decreases the 
strength. 

* American Text-book of Prosthetic Dentistry. 



METALS OF GROUP V. 63 

Various methods have been prepared to overcome the diffi- 
culties in manipulation of plaster, such as mixing the plaster 
with alum, marble-dust, or potassium sulphate. A compound 
on the market consists of a mixture of plaster and Portland 
cement. A mixture which has been very strongly recommended 
as an investment preparation consists of two-thirds plaster and 
one-third powdered pumice-stone. 

Analytical Reactions. — Use a 3 or 4% solution of CaCl 2 
for tests. 

CaCl 2 with (NH 4 )2C0 3 gives white precipitate of CaC0 3 , 
easily soluble in acids. 

CaCl2 with oxalic acid or soluble oxalates gives a white pre- 
cipitate of CaC20 4 , similar in form to the SrC20 4 but much more 
difficult to obtain in the crystalline condition. 

CaS0 4 is not precipitated except from moderately concen- 
trated solution. 

A saturated solution of CaS0 4 may be used to test for stron- 
tium salts in presence of Ca. 

Magnesium, Mg. 

Atomic weight 24.36. Burns easily in the air, forming MgO. 
Principal sources are the carbonate, MgC0 3 , magnesite, and a 
double carbonate, CaMg(C0 3 ) 2 , dolomite. The sulphate MgS0 4 
occurs in the mineral kieserite in the "Stassfurt deposit." 
"French chalk" (or talcum), soapstone, and meerschaum con- 
sist of magnesium silicate in varying states of purity. 

Asbestos is a double silicate of magnesium and calcium. 

Compounds. — Epsom salt, or magnesium sulphate, occurs 
as a constituent of laxative waters. The crystallized salt, 
MgS0 4 -7 H 2 resembles oxalic acid in appearance, and has been 
mistaken in several instances for the poisonous acid. 

Magnesium carbonate is used in pharmacy in two forms; 
viz., the light and the heavy. These are produced by precipi- 



64 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

tating dilute or concentrated solution of magnesium sulphate 
with sodium carbonate. 

The light and heavy magnesium oxides are produced by 
calcination of the light or heavy carbonates. Magnesium salts 
are quite generally distributed in the human system, but in 
small quantities. They occur in the bones, the teeth, and the 
various body fluids. 

Analytical Reactions. — A 5% solution of the sulphate or 
nitrate may be used in the following tests : 

Magnesium salts with (NH 4 ) 2 C0 3 give a white precipitate 
of basic carbonate of variable composition. This precipitate 
forms very slowly in dilute solution, and in the presence of 
NH4CI the formation of soluble double salts prevents the pre- 
cipitation altogether. 

MgCl 2 with Na 2 HP0 4 gives in fairly concentrated solution 
a white precipitate of MgHP0 4 . In presence of NH 4 C1 and 
NH4OH the alkaline phosphates precipitate magnesium-ammo- 
nium-phosphate, MgNH 4 P0 4 ,6H 2 0, even from very dilute solu- 
tion (Plate IV, Fig. 2). 

In case the precipitate has formed very slowly, it may separ- 
ate as small, almost transparent, crystals clinging to the sides 
of the beaker. 

Ammonium oxalate does not precipitate magnesium solu- 
tions. 

Analysis of Group V. 

(Ba, Sr, Ca, Mg.) 

To the filtrate from Group IV containing NH 4 C1 and NH 4 OH, 
add (NH 4 ) 2 C0 3 . (If NH 4 C1 and NH 4 OH are not present, add 
10 c.c. of NH 4 C1 solution and NH 4 OH till strongly alkaline before 
proceeding with the analysis.) Ba, Sr, and Ca will be pre- 
cipitated as carbonates; Mg will be held in solution by the 
ammonium chlorid. Filter. 



METALS OF GROUP V. 




Ca, Ba, Sr carbonates. 



Alg. and metals of Group VI. 



Test the filtrate for Mg by adding Na 2 HP0 4 , when a white 
crystalline precipitate is NH 4 MgP0 4 ,6 H 2 0. 

To the carbonates on the paper add dilute acetic acid, 
which will dissolve the precipitate, forming acetates of the three 
metals. 

Take a portion of the acetate solution in a test-tube and 
make a preliminary test for Ba by adding acid chroma te 
of potassium (K 2 Cr 2 7 ). A yellowish precipitate will be 
BaCr0 4 . 

If Ba is present, add K 2 Cr 2 7 to the whole of the solution 
and filter out the BaCr0 4 . 




BaCr0 4 . 



Sr and Ca acetates, K2O2O7, etc. 



It is desirable to remove the excess of bichromate from the 
nitrate before testing for Ca and Sr.* To do this add NH 4 OH 
till alkaline; then (NH 4 ) 2 C03 will precipitate SrC03 and CaCOa. 
Filter and dissolve off the paper with acetic acid as before. 

* The object of removing the K 2 Cr?07 is to furnish a colorless solution wherein 
the Sr or Ca precipitates may be more clearly discerned. It is not absolutely 
necessary and, in case the amount of Sr and Ca is probably slight, might be omitted, 
as the operation is always attended with some loss. 



66 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




CaCCb and SrC03, which when treated with acetic acid, will 



give a solution of the acetates of Ca and Sr. 



Reserve about one-fourth of this acetate solution. To the 
remainder add dilute K 2 S0 4 solution, which will precipitate 
SrS0 4 . (If only slight amounts of Sr are present, it may take 
some time to complete the precipitation. If a large amount 
of Ca is present, some CaS04 may also be thrown down.) Filter. 




SrS0 4 . 



Ca(C 2 H 3 02)2 or CaS0 4 . 



Test filtrate for Ca by adding ammonium oxalate, which 
will precipitate calcium oxalate, white. 

If there is any question about the precipitate thrown out 
by K 2 S0 4 being Sr, make confirmatory test on reserved portion, 
either by flame test (page 61), or by adding CaS0 4 , and allow- 
ing to stand twelve hours. CaS0 4 will precipitate Sr as SrS0 4 , 
but of course cannot precipitate Ca. 



QUESTIONS ON GROUP V. 

Why add NH 4 C1 before precipitating the group with 
(NH 4 ) 2 C0 3 ? 

Why dissolve the precipitated carbonates in acetic acid 
rather than HC1? 



METALS OF GROUP V. 67 

Why use the acid chromate of potassium (K 2 Cr 2 7 ) in 
testing for Ba rather than the neutral chromate (K 2 Cr0 4 ) ?. 

Why precipitate Sr and Ca after separation of Ba with 
K 2 Cr 2 7 ? 

Laboratory Exercise XVII. 

The Alkaline Earths. 

Exp. 30. To a little clear lime water add a few drops of 
ammonium carbonate solution. 

Ca0 2 H 2 + (NH 4 ) 2 C0 3 = ? 

Will an excess of reagent dissolve this precipitate? If C0 2 
were used in place of (NH 4 ) 2 C0 3 would the solubility of the 
precipitate be the same ? Why ? 

Exp. 31. Take in separate test-tubes about 5 c.c. of each 
of the following dilute solutions: CaCl 2 , BaCl 2 , Sr(N0 3 ) 2 , and 
MgCl 2 . Add to each 1 or 2 c.c. of NH 4 C1 solution, and then a 
little (NH 4 ) 2 C0 3 solution. 

Now add cautiously to each tube, containing a precipitate, 
dilute acetic acid till the precipitates are all dissolved. To each 
of these three tubes add a few drops of K 2 Cr 2 7 solution. 

Write the reactions. Formulate a method for the separation 
of Ca, Ba, and Mg from a mixture containing all three. 

Exp. 32. To a solution of magnesium chlorid add a little 
NH 4 OH and NH 4 C1 solution and lastly some sodium phosphate. 

The formula for the precipitate is NH 4 MgP0 4 . Complete the 
reaction. 

MgCl 2 + Na 2 HP0 4 + NH 4 OH = 

Exp. 33. To each of the four solutions used in Exp. 31 add 
a little dilute H 2 S0 4 . 

Which of the four metals forms the least soluble sulphate ? 

Which the most soluble ? 

Exp. 34. To a solution of Sr(N0 3 ) 2 add a solution of CaS0 4 
and allow to stand. 



68 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Exp. 35. To a solution of a calcium salt add some ammo- 
nium oxalate solution. Write reaction. 

Exp. 36. In a watch glass place a few drops of lime-water, 
in another place some baryta water. Set the two glasses aside 
for a while and explain any change that takes place. 

Exp. 37. Make flame tests with solutions of barium, stron- 
tium, and calcium. 

Laboratory Exercises XVIII, XIX, and XX. 

Unknown solutions. Metals of the various groups thus far 
considered. 



CHAPTER VIII. 
METALS OF GROUP VI. 

The Alkaline Metals, K, Na, NH, Li. 

Potassium, sodium, and the hypothetical " metal" ammo- 
nium are the bases of a very large number of salts used in the 
arts and sciences. 

As a class the metals may be distinguished from the alkaline 
earths by the ready solubility of their hydrates and carbonates. 
The hydrates of the alkaline earths are only sparingly soluble, 
and their carbonates are insoluble. 

The salts of lithium are also soluble, but are used in relatively 
small amounts. 

These bases are not precipitated by any group reagent and 
must be detected by individual tests. 

Potassium, K (Kalium). 

Atomic weight 39.15. Occurs as carbonate in wood ashes, 
as nitrate in the "nitre beds" of India, etc., as chlorid from the 
Stassfurt deposit in the Province of Saxony, Prussia, as the 
mineral sylvite, also in the double chlorid of Mg and K (car- 
nallite) . 

The salts of potassium are generally soluble in water. Among 
the more important compounds is the hydroxid KOH. This 
is used very largely as a starting point in the preparation of 
many of the medicinal salts of potassium. It may be made by 
treating potassium carbonate with slaked lime, according to the 
following reaction: 

Ca0 2 H 2 + K 2 C0 3 = CaC0 3 + 2 KOH. 

69 




70 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The carbonate obtained from wood ashes is known as salts 
of tartar, and in the impure form as pearl ash. Potassium car- 
bonate is also made in large quantities from the native chlorid 
found in the Stassfurt deposit. 

The bicarbonate KHC0 3 , or saleratus, may be obtained by 
saturating the carbonate with C0 2 . 

K 2 C0 3 + C0 2 + H 2 = 2 KHCO3. 

This salt, used in cooking, proves more or less irritating, and has 
been practically replaced by the corresponding sodium salt, 
NaHC0 3 or "cooking soda." 

Potassium nitrate, KN0 3 , also called nitre and saltpeter is 
used in medicine as a diuretic. It gives off oxygen easily, and 
is consequently a good oxidizing agent, and as such is a con- 
stituent of fireworks, gunpowder, etc. 

KNO3 may be prepared from the cheaper sodium nitrate by 
double decomposition with potassium chlorid. 

NaN0 3 + KC1 = KNO3 + NaCl. 

Potassium bromid, used as a sedative, may be prepared by 
treating caustic potash, KOH, with bromin. 

6 Br + 6 KOH = 5 KBr + 3 H 2 + KBr0 3 . 

The bromate, KBr0 3 , is separated by crystallization. 

Potassium iodid may be made in a similar manner by sub- 
stituting iodin for the bromin. Potassium iodid is very sol- 
uble, being dissolved in less than its own weight of water. 
In the laboratory potassium iodid is used as a solvent for iodin, 
and as a reagent. 

Potassium cyanid, KCN, an extremely poisonous compound, 
is used by jewelers for cleaning silver, etc., and in the arts for 
the preparation of double salts used in electro-plating. It is 
decomposed by C0 2 , forming K 2 C0 3 and liberating hydrocyanic 
acid. 

Potassium chlorate may be prepared by treating a hot solution 



METALS OF GROUP VI 71 

of the hydroxid with chlorin gas. The reaction is the same 
as that given for the preparation of the bromid, and results 
in five molecules of the potassium chlorid to one of the chlorate. 

Potassium sulphid, K 2 S, is soluble in water and in common 
with other alkaline sulphids, is a solvent for sulphur, thereby 
forming a number of polysulphids. 

The pentasulphid, K 2 S 5 , is known as liver of sulphur or 
sulphuret of potassium. 

Potassium platinic chlorid, K 2 PtCl 6 , and potassium acid 
tartrate, KHC 4 H 4 6 , are only sparingly soluble and may be 
precipitated by addition to the solution of an equal volume of 
alcohol, in which they are quite insoluble. 

The potassium acid tartrate, or bitartrate, is also called 
cream of tartar, and is used in the manufacture of baking powder. 
This salt separates from wine vats, it being precipitated by the 
alcohol produced during the process of fermentation of the 
grape juice. In this impure form it is known as argols, or 
crude tartar. 

Analytical Reactions. — The presence of potassium salts 
may be detected spectroscopically or by the violet color given 
to the flame observed through blue glass. Make comparative 
tests with known solutions of sodium and potassium salts, using 
blue glass of sufficient thickness to obscure the yellow (Na) ray. 

Note. — In making the flame test the best results are obtained by evaporating a 
little of the original solution to dryness, moistening with HC1 and then taking 
up on a loop of clean platinum wire. 

The platinic chlorid test may be made as follows: 
Add a few drops of HC1 to a little of the solution, then 
evaporate to dryness. Keep at a low red heat till all ammo- 
nium salts have been driven off, cool, and take up in a little 
(not more than 5 c.c.) distilled water. Add a few drops of 
H 2 PtCl 6 and about 5 c.c. of alcohol. Set aside for some time. 
K 2 PtCl 6 , yellow, will crystallize out recognizable under the 
microscope (Plate III, Fig. 3). 



72 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Sodium, Na (Natrium). 

Atomic weight 23.05. Occurs principally as chlorid in sea- 
water and in mineral deposits, and to a lesser extent as nitrate, 
Chili saltpeter, and as cryolite, the double fluorid of Al and Na, 
(Na 3 AlF 6 ), found in Greenland. 

Compounds. — Sodium peroxid, or dioxid, Na 2 2 , may be 
prepared by simply heating metallic sodium in dry air. It is a 
yellowish white powder used somewhat in dental practice for 
the preparation of alkaline solutions of H 2 2 : 

Na 2 2 + 2 H 2 = 2 NaOH + H 2 2 . 

The alkaline peroxid is much more efficient as a bleaching agent 
than the neutral or acid preparations. 

Sodium hydroxid, NaOH, is found in trade in several forms. 
The stick " caustic soda, " used in chemical laboratories, contains 
anywhere from 5 to 30 per cent of water. In a powder form, 
less pure than the above, it is known as "concentrated lye," 
Babbitt's potash, etc., and is used for cleaning, and in the manu- 
facture of soap. NaOH is caustic or escharotic in its action upon 
animal tissue. It may be made experimentally by experiment 
No. 39, page 78. 

Sodium carbonate, Na 2 C0 3 , crystallizes with ten molecules 
of water. In this form it is known as "sal soda," or washing 
soda. It is used as a starting point in the manufacture of other 
sodium salts. Sodium carbonate is produced from NaCl by 
the LeBlanc process, in which the following reactions are in- 
volved : 

(1) 2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1. 

(2) Na 2 S0 4 + 2 C = Na 2 S + 2 C0 2 . 

(3) Na 2 S + CaC0 3 = Na 2 C0 3 + CaS. 

The last two reactions are combined in the actual process of 
manufacture, and the mixture of sodium sulphate, carbon, and 
calcium carbonate are heated together with the resulting forma- 



METALS OF GROUP VI. 73 

tion of "black ash" from which is produced pure sodium 
carbonate. 

More recent processes are the Solvay or Ammonia process, 
depending on the following reaction: 

NaCl + NH 3 + C0 2 + H 2 = NaHC0 3 + NH 4 C1. 

and the cryolite process in which the source of the sodium is the 
double fluorid of sodium and aluminum, Na 3 AlF 6 . By this 
process the cryolite is heated with lime, forming calcium fluorid 
and sodium alumina te. 

Na 3 AlF 6 + 3 CaO = 3 CaF 2 + Na 3 A10 3 . 

Note. — According to Remsen the sodium aluminate probably consists of a 
variety similar in composition to the potassium aluminate given on page 46, 
(NaA102 and Na 2 until water is added). 

Sodium bicarbonate, NaHC0 3 , also called cooking soda, is 
largely used like "saleratus" (KHC0 3 ) as a source of C0 2 in the 
leavening or aerating of bread. 

Sodium bicarbonate is hydrolized by water, i.e., it dissociates 
in solution forming NaOH and H 2 C0 3 . The carbonic acid is a 
weak acid furnishing very few hydrogen ions, while the hydroxid 
is a strong base. It follows that the reaction of such a solution 
is alkaline to litmus, although the salt answers to our definition 
of an acid salt. This is true of Na 2 C0 3 (the products of dis- 
sociation being NaOH and NaHC0 3 ) , and in a similar manner of 
corresponding potassium salts. 

Sodium chlorid, NaCl, common salt, exists in sea-water to 
the extent of 2.7%, and is, to some extent, obtained from this 
source, although the greater amount is produced by the salt mines. 
Salt is a constituent of all of the body fluids, and can be easily 
obtained as cubical crystals by the evaporation of urine or of 
dialyzed saliva. 

Physiological, or normal salt solution, contains about 0.7% 
NaCl, and has practically the same osmotic pressure as blood. 



74 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

The term "physiological" is to be preferred to the term 
"normal," as normal salt solution is also properly applied to a 
solution used in volumetric analysis containing exactly 5.85% 
NaCl (see page 149). 

Sodium nitrate, NaN0 3 , Chili saltpeter, is valuable as a ferti- 
lizer, but too hygroscopic to be used in the same way as potas- 
sium nitrate, in the preparation of gunpowder, fireworks, etc. 

Sodium phosphate, trisodic phosphate, Na3P0 4 , is a crystal- 
line salt, soluble in water, but of slight interest in Dental Chem- 
istry. It is easily decomposed by C0 2 , forming Na 2 HP04 and 
Na 2 C0 3 . 

2 Na 3 P0 4 + H 2 + C0 2 = 2 Na 2 HP0 4 + Na 2 C0 3 . 

The disodic phosphate, Na 2 HP0 4 , also called neutral or 
orthosodium phosphate, is the sodium phosphate of the Pharma- 
copoeia. It is faintly alkaline in reaction, and exists in the body 
fluids generally. The alkaline reaction (to litmus) of saliva 
is, in part, due to its presence. 

The acid, or monobasic sodium phosphate, NaH 2 P0 4 , is a 
translucent crystalline salt found to some extent in the body 
fluids, particularly the urine, to the acidity of which it is prob- 
ably a contributing factor, although to a much less extent than 
was formally supposed. 

Sodium potassium tartrate, KNaC 4 H 4 6 , Rochelle salt, is 
used in medicine as a mild laxative. It is the product of the 
double decomposition incident to raising bread with "cream of 
tartar and soda." 

KHC 4 H 4 6 + NaHC0 3 = KN 2 C 4 H 4 6 + C0 2 + H 2 0. 

Sodium sulphate crystallized with ten molecules of water 
(Na 2 S0 4 io H 2 0) is known as Glauber's salt. 

Analytical Reactions. — Na may be detected by the use of the 
spectroscope or by the persistence of the yellow flame obtained 
with a clean platinum wire and a colorless Bunsen flame. Make 
a comparative test with small amount of known sodium salt. 



METALS OF GROUP VI. 75 

Sodium salts are soluble with only a very few exceptions. 
The pyroantimonate, Na 2 H 2 Sb 2 07, may be precipitated in the 
cold by a freshly prepared solution of potassium pyroanti- 
monate. (Prescott and Johnson, p. 228.) 

From a solution stronger than 3% and nearly neutral the 
double acetate of uranyl and sodium (NaC2H30 2 ,U02(C2H 3 02)2) 
may be precipitated. (Plate IV, Fig. 6.) As triple crystalline 
acetates may also be formed with Mg, Cu, Fe, Ni, and Co, it 
is recommended to first precipitate the bases of the first five 
groups and drive off ammonium salts, as in the test for K with 
H 2 PtCl 6 .* 

Lithium, Li. 

Atomic weight 7.03. The carbonate, citrate, bromid and 
chlorid are used in medicine. 

The value of lithium salts as uric acid solvents is question- 
able, because of the insolubility of the phosphate (page 237). 

The presence of lithium is easily shown after the precipita- 
tion of strontium by the intense carmine color given to the 
Bunsen flame. 

The spectroscope furnishes a very delicate and positive test 
for this element. 

Ammonium, NH 4 . 

Ammonia is obtained in large part from the ammoniacal 
liquor of the gas works, where illuminating gas is made by the 
distillation of coal. The liquor, charged with ammonia, is 
treated with hydrochloric or sulphuric acid, thus producing an 
impure salt which is subsequently purified or used as a source 
of NH 3 in the preparation of pure ammonium compounds. 

(NH 4 ) 2 S0 4 + Ca0 2 H 2 = CaS0 4 + 2 NH 3 + 2 H 2 0. 

* Behrens's Manual of Microchemical Analysis, page 32. 



;() SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Compounds. — Ammonium hydroxid, NH 4 OH, has never 
been separated as such, free from water. It undoubtedly ex- 
ists, however, in aqueous solutions of ammonia gas. 

NH 3 + H 2 = NH4OH. 

The negative hydroxyl ions of this ammonium base do not dis- 
sociate to the same degree as takes place in solutions of KOH; 
hence, it is a weaker base. 

Aqua ammonia of the pharmacopoeia contains 10% NH 3 . 
The "stronger water of ammonia" contains 28% of the gas, 
which is about as strong a solution as it is safe to make for 
shipment, and containers should never be more than four- 
fifths full. The 28% solution is referred to as 26 ammonia, 
the degree indicating the specific gravity as taken by the Baume 
hydrometer. 

Ammonium carbonate exists in solution. The salt used in 
medicine under this name is really a mixture of ammonium 
bicarbonate, NH4HCO3, and the carbamate, NH 4 NH 2 C0 2 . 

This salt gives off NH 3 gas, and moistened with ammonia 
water and perfumed constitutes "smelling salts." 

Ammonium chlorid, sal ammoniac (NH 4 C1), white crystal- 
line, is made by neutralizing NH 4 OH with hydrochloric acid. 
Ammonium chloride will sublime unchanged. It is freely sol- 
uble in water, and its solution acts as an electrolyte and will 
dissolve metals from an alloy. If a silver spoon or a 10-cent 
piece is allowed to remain for 10 or 12 hours in a dilute 
solution of NH4CI, an appreciable amount of copper will pass 
into solution, coloring it blue or green, according to the con- 
centration of the copper solution. It also dissolves some me- 
tallic oxides, as ZnO. 

As saliva is known to contain considerable NH 4 C1, the 
above facts should be studied carefully in considering the action 
of saliva on substances used for filling teeth, although the solvent 
action of NH 4 C1 in saliva is nothing like what it is in water. 



METALS OF GROUP VI. 77 

Ammonium nitrate, NH 4 N0 3 , crystallizes in large six-sided 
prisms without water of crystallization. It is very soluble in 
water. It melts at 165 C. Heated to 210 C, it decom- 
poses into nitrous oxid and water. Above 250 C, other oxids 
of nitrogen are produced, so in the preparation of nitrous oxid for 
dental anesthesia, care should be taken to keep the temperature 
of the reaction between these limits. 

Ammonium acetate, NH4C2H3O2. A solution of this salt, 
containing about 7%, is used in medicine as a diaphoretic. 
The solution is also known as Spirit of Mindererus. In analyti- 
cal chemistry, it is used as a solvent for lead sulphate. 

Ammonium sulphate, (NH 4 ) 2 S0 4 , is a white crystalline salt 
soluble in water, not used medicinally, but largely used as a 
reagent in physiological chemistry. It melts at 140 C, and 
at a higher temperature it decomposes. 

Ammonium sulphid, (NH 4 ) 2 S, is used as a solvent and 
reagent. It may be prepared by saturating ammonia water, 
NH4OH, with H 2 S, then adding an equal volume of ammonia 
water : 

NH 4 OH + H 2 S = NH 4 SH + H 2 0, 

and NH 4 SH + NH 4 OH = (NH 4 ) 2 S + H 2 0. 

A polysulphid, made by dissolving sulphur in (NH 4 ) 2 S is 
the reagent used in dissolving the sulphids of Group II (b) and 
in precipitating the zinc group. 

Ammonium phosphates. Ammonium, like other univalent 
bases, is capable of forming, with phosphoric acid, three differ- 
ent salts. (NH 4 ) 3 P0 4 is very unstable. The diammonium 
phosphate has been used, to a slight extent, in medicine (BrP) 
and has been shown to be an energetic activator of lactic acid 
organisms.* 

The importance of this fact, in relation to dental caries, has 
yet to be demonstrated. 

* Dr. Percy Howe in Dental Cosmos, Jan., 191 2. 



78 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Microcosmic salt is a name given to a double ammonium so- 
dium phosphate (NH 4 NaHP0 4 *4 H 2 0) used in blowpipe analysis. 

Analytical Reactions. — Ammonium salts are generally sol- 
uble. H 2 PtCl 6 precipitates the double chlorid (NH 4 ) 2 PtCl 6 , 
similar in appearance and crystalline form to the corresponding 
potassium salt (Plate III, Figs. 1-3). 

Ammonium salts are most easily detected by the evolution 
of ammonia gas (NH 3 ) whenever they are heated with fixed 
alkali, NaOH or KOH. 

The test may be made upon the original solution by boiling 
in a test-tube with a little 10% NaOH, and the escaping NH 3 
may be detected by the odor or, better, by suspending in the 
upper part of the tube a piece of moistened red litmus paper,* 
which is promptly turned blue by the " volatile alkali." The 
litmus-paper test is more delicate than the odor test. Care 
should be taken that the paper does not touch the sides of the 
tube, as it may come in contact with traces of NaOH. 

Many ammonium solutions give off NH 3 gas without the 
aid of any fixed alkali. Common examples are the carbonate, 
acid carbonate, hydrate, sulphid, and sulphydrate. 

Laboratory Exercise XXL 
The Alkali Metals. 

Exp. 38. In 10 or 15 ex. of water contained in a porcelain 
dish, dissolve a small piece of metallic potassium. 
1 Stand well away from the dish as the reaction may result in 
spattering hot water or hot metal. 

Test resulting solution with red litmus paper. Write reac- 
tion. 

Exp. 39. Take a little strong solution of carbonate of soda 
(about 20% of crystallized salt), heat nearly to boiling in a 
porcelain dish, then add about half as much milk of lime (made 

* Blue paper may be reddened by leaving it a few hours in a wide-mouth 
bottle after wetting the under side of the stopper with a drop or two of acetic acid. 



METALS O'F GROUP VI. 79 

of one part Ca(OH) 2 to four parts water). Continue the boil- 
ing for several minutes, then allow to settle. Decant the clear 
liquid. 

Test the liquid with various indicators. Is it acid or alka- 
line? 

To a small portion of it add a few drops of HC1. Does it 
effervesce? Test in a similar manner the carbonate of soda 
solution 

Na 2 C0 3 + CaH 2 2 = ? 

Which of these two compounds used is a base ? 

Which an alkali? 

Exp. 40. In separate test-tubes heat the following mixtures: 

1. Solution of NH4CI and solution of NaOH. 

2. Solution of (NH 4 ) 2 S0 4 and solution of KOH. 

3. Dry NH4CI and dry Ca0 2 H 2 . 

In each case note the odor of the gas evolved and test the 
vapor with moistened red litmus paper and write the reaction. 

Exp. 41. Take three test-tubes and into one put about 
5 c.c. of a dilute solution NaCl; into the second, KC1; and into 
the third, NH 4 C1; then to each add a few drops of platinic 
chlorid solution and allow to stand till the next exercise. 

Exp. 42. Make flame tests according to directions given in 
the lecture room, with salts of sodium, potassium, and lithium. 

Exp. 43. Place in an ignition tube one or two grams of 
potassium tartrate and heat till no further change takes place. 
Cool and dissolve in water. Test a portion of the resulting 
solution with a few drops of HC1. In like manner test the 
original tartrate. 

Note. — In general, the ignition of salts of organic acids results in the for- 
mation of carbonates. 

Exp. 44. Make a spectroscopic examination of solutions of 
Na, K, Li, Ba, Sr, and Ca, and describe the bands observed. 



So SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Note. — This experiment is only to be performed under the direction of an 
instructor. Opportunity will be given for this experiment during the next exer- 
cise if necessary. 

Laboratory Exercises XXII and XXIII. 

Analyses of Solutions Containing all Bases. 

Analysis of Groups III, IV, and V. 

When phosphates, borates, or oxalates are present. 

To the filtrate from Group II add NH 4 C1 and NH 4 OH in 
slight excess. Heat to boiling and add (NH 4 ) 2 S slowly (always 
keeping the solution at the boiling-point) until precipitation is 
complete. Filter as rapidly as possible and wash with hot 
water, adding occasionally a little (NH 4 ) 2 S. 

The filtrate, which may contain the barium and potassium 
groups, must be concentrated by evaporation, filtered if neces- 
sary, and set aside.* The precipitate may contain MnS, ZnS, 
CoS, NiS, FeS, Al(OH) 8 , and Cr(OH) 3 with phosphates or 
oxalates soluble in acids only. The color of the precipitate 
will give some indication of what is present. Test the pre- 
cipitate for Mn by fusing a part with KN0 3 and Na 2 C0 3 . 

Treat the precipitate with cold dilute HC1 in which CoS 
and NiS alone are insoluble. Filter. Treat insoluble residue 
for Co and Ni according to directions on page 56. 

The HC1 solution, which may contain Mn, Zn, Fe, Cr, and 
Al as chlorids, and phosphates and oxalates soluble in acids, and 
which is green or violet if much Cr is present, is boiled with a 
few drops of HN0 3 until all the H 2 S is expelled. 

Test a small portion of the solution for Fe exactly as in 
analysis of Group III given on page 48. Of the remainder of 
the solution take about one-third, and add dilute H 2 S0 4 . 

* If Ni is present, the nitrate is frequently brown or black, since NiS is some- 
what soluble in an excess of (NH 4 ) 2 S, especially if much NH 4 OH is present. The 
NiS may be precipitated, after evaporation, by acidifying with HC1. 






METALS OF GROUP VI. 



81 



A white precipitate may contain BaS0 4 , SrS0 4 , and pos- 
sibly CaS04. Filter, wash precipitate, and fuse with a mixture 
of Na 2 C0 3 and K 2 C0 3 , 

Note. — The mixture of the two carbonates in molecular proportions fuses at 
a lower temperature than either salt alone. 

Filter and wash the carbonates thus formed, dissolve them 
in acetic acid and examine this solution for Ba, Sr, and Ca 
as directed under the Ba group. To the filtrate from the pre- 
cipitate produced by H 2 S0 4 , or to the solution in which H 2 S0 4 
has failed to give a precipitate, add three times its volume of 
alcohol; Ca, if present, is precipitated as white CaS0 4 , and its 
presence may be confirmed by dissolving the precipitate in 
water and adding (NH 4 ) 2 C 2 4 , which precipitates CaC 2 4 , 
white. 

To the rest of the HC1 solution add ferric chlorid, carefully, 
till a drop of the solution gives, when mixed with a drop of 
amnionic hydrate, a yellowish precipitate. To the solution add 
Na 2 C0 3 or K 2 C0 3 till the acid is nearly neutralized, then add 
excess of freshly precipitated BaC0 3 , and allow to stand over 
night. Filter. 




Cr and Al as hydrates. (Fe as phosphate or hydrate and 
BaC0 3 .) 



MnCl 2 , ZnCl 2 , and possibly members of Group V. 



Transfer the precipitate to a small beaker and boil for 
some time with NaOH or KOH. The Al will be converted 
into the alumina te KA10 2 . The phosphate will be more or 
less completely changed to potassium or sodium phosphate. 
Filter. 



82 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 




Cr(OH) 3 , BaC0 3 , etc. 



KAIO2 and Na 2 HP0 4 . 



Test precipitate for Cr as on page 48. Add HNO3 to fil- 
trate till acid, then divide into two parts; test one for P 2 & 
with (NH 4 ) 2 Mo0 4 . 

Test the other for Al by adding NH 4 OH till alkaline, when 
precipitate will be A1P0 4 , insoluble in acetic acid. 

To the solution of Mn and Zn chlorids add a little HO 
and boil. Then make alkaline with NH 4 OH, add (NH^S, 
warm slightly and filter. The precipitate (MnS and ZnS) may 
be dissolved in cold dilute HC1 and tested for Mn and Zn as in 
analysis of Group IV, page 56. 

OUTLINE SCHEME FOR ANALYSIS OF GROUP I. 

To about one-third of a test-tubeful of the unknown solution add a few drops 
of HC1. 

Ppt. = AgCl, HgCl, PbCla. Add hot H 2 0. 



Residue =AgCl, HgCl. 
Add NH 4 OH. 



Residue = HgCl. 
Test, page 20. 



Solution =AgCl. 
Test with HN0 3 . 



Solution = PbCl 2 . 
Test as on page 19. 



METALS OF GROUP VI. 



83 



OUTLINE SCHEME FOR ANALYSIS OF GROUP II. 

To the warmed filtrate from Group I add H2S. A ppt. may be sulphids of 
As, Sb, Sn, Au, Pt, Cu, Cd, Bi, Hg, and Pb. 
Filter and treat with warm (NH 4 ) 2 S. 



Residue is Group II (a), page 38, and consists 

of sulphids oi'Cu, Cd, Bi, Hg, and Pb. 
Treat on paper c warm dil. HN0 3 . 



Solulion=As, Sb, Sn, Au, and Pt. Reprecipitate 
c HC1. filter and treat ppt. c strong (NH 4 ) 2 C0 3 
sol. 



Residue 

isHg. 

Dissolve 

in aqua 

regia and 

test c 

SnCl 2 

(page 38). 



Solution Cu, Cd, Bi, and Pb. 
Add H 2 S0 4 and filter. 



Ppt. 

is 
PbS0 4 



Solution is Cu, Cd, and 
Bi. AddNH 4 OHand 

filter. 



Ppt. is 
Bi(OH) 3 



Solution is Cu and 
Cd. 



Test for 
Cue HA 

and 
K 4 FeCy 6 

(page 39 



Test for 
CdcKCN 
and H 2 S. 



Residue=Sb, Sn L Au, and Pt, sul- 
phids. Treat c cone. HC1, dilute 
and filter. 



Residue. 
Au and Pt. Dissolve 
in aqua regia and di- 
vide. 



Pt. I. 

Test for 

Au c FeS0 4 

(p. 40). 



Pt. II. 

Test for 

Ptc 
NH 4 C1 
and alco- 
hol. 



Solution. 

Sb and Sn. 
Test for 
SbcPt 

foil and Zn. 



Test for 
Sn in fil- 
trate c 
HgCl 2 
(p. 40). 



Solution. 

As. Make 
Gutzeit's 
or Fleit- 
mann's 

test for As 
(page 28). 



OUTLINE SCHEME FOR ANALYSIS OF GROUPS III AND IV. 

Take the clear solution in which H 2 S fails to produce a precipitate and boil 
with a few drops of HNO3 till H 2 S is expelled. Add NH 4 C1 and NH 4 OH. Filter. 



Precipitate = Group III. Fe, Al, and Cr. Fuse 
c Na 2 C0 3 and KN0 3 . Boil c H 2 and 
filter. 



Residue = 

Fe. Test for 

Fe c KCyS 

and 

K 4 FeCy 6 

(page 48). 



So/m^'o«= Aland Cr. Divide 
solution and 



Test for Al 
with HC1 

and 

(NH 4 ) 2 C0 3 

(page 48) 



Test for Cr 
with acetic 
and lead ace- 
tate (page 
48). 



Solutions= Groups IV, V, and VI. Add (NH 4 ) 2 S 
and precipitate. Group IV — Co, Ni, Mn, 
and Zn. Treat with cold dilute HC1. 



Residue = Co 
and Ni. Make 
borax-bead 
test. Sepa- 
rate Co by 
means of 
KNO., (page 
56). 



Solution=Mn and Zn. Boil 
and treat c KOH or NaOH. 



Precipitate = 

Mn(OH) 2 . 

Make red-lead 

test for Mn 

(page 53). 



Solution = 

K,Zn0 2 . Test 

for Zn c H 2 S 

or (NH 4 ) 2 S 

(page 57). 



S4 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

OUTLINE SCHEME FOR ANALYSIS OF GROUPS III, IV, AND V. 

(Phosphates, oxalates, borates, etc., being present.) 
To filtrate from Group II add NH 4 C1 and NH 4 OH. Heat and add (NH 4 ) 2 S. 
Filter rapidly. 



Precipitate=MnS, ZnS, CoS, NiS, FeS, Al(OH) 3 , Cr(OH) 3 , also phosphates, etc., 
soluble in acids only. Fuse part of precipitate and test for Mn (page 57). Treat 
remainder c cold dilute HC1. 



Residue = 

CoS and 

NiS. Make 

borax-bead 

test and 
separate Co 
if neces- 
sary, c 
KNO, 
(page 56). 



Solution = Mn, Zn, Cr, and Al. Divide solution into three parts of 
about 1/8, 2/8, and 5/8, respectively, and treat as follows: 



Filtrate, 

members of 

Ba and K 

groups. 



I. 

Test 

small 

portion 

forFe 

(page 48). 



II. 

To second portion add di- 
lute H 2 S0 4 . 



Precipitate 
may be 
BaS0 4 , 
SrS0 4 or 
CaS0 4 . Fil- 
ter, wash, 

fuse c 
Na 9 C0 3 and 
K2CO3. Dis- 
sol ve fu sion 
in HA and 
analyze for 
Group V. 



Solution^ 
CaS0 4 . 

Add alco- 
hol; if pre- 
cipitate oc- 
curs, filter, 
dissolve in 

H 2 0, and 

test with 
ammonium 

oxalate. 



III. 

To third portion add FeCl 3 to combine 
c H 3 PO.„ etc., then add Na 2 C0 3 or 
K 2 C0 3 , and BaC0 3 (page 81). 



Precipitate=Cr, Al, Fe, and 
BaC0 3 . Boil precipitate 
c NaOH and filter. 



Residue = 
Cr, BaC0 3 , 

etc. Test 

for Cr as on 

page 48. 



Solution^ 

KA10 2 . 
Test for Al 
as on page 



Solution= 

Mn and Zn. 

Reprecipi- 

tate Mn 

and Zn as 

sulphids, 

and test 

according to 

page 56. 



OUTLINE SCHEME FOR ANALYSIS OF GROUPS V AND VI. 
To the clear filtrate from Group IV add (NH 4 ) 2 C0 3 . 



Precipitate=Ba., Sr, and Ca. Add K 2 Cr 2 7 if necessary to pre- 
cipitate Ba. 



Precipitate=BaCrO i 



Solution = Sr and Ca. Reprecipi- 
tate Sr or Ca with (NH 4 ) 2 C0 3 
and test, or CaS0 4 . Remove 
Sr with K 2 S0 4 and alcohol, and 
test filtrate for Ca with(NH 4 ) 2 - 
C 2 4 (page 66). 



Solution=Mg and Group VI. 
Test for Mg with Na 2 HP0 4 
(page 65). Make separate 
tests for metals of Group 
VI according to pages 71, 74, 
and 78 of the text. 



CHAPTER IX. 

ANALYTICAL REACTIONS OF THE ACIDS. 

In the analytical processes thus far described we have con- 
sidered only the separation and detection of the basic or metallic 
part of the salt, that is, we have analyzed a solution of ferric 
chlorid and found the iron only. It is necessary to find the 
chlorin. Before making any examination for acid, it will be 
possible to save a considerable amount of both time and labor 
by first carefully considering what acids are capable of forming 
soluble salts with the bases which have already been detected. 
To facilitate this consideration a table of solubilities will be found 
below and on the following page, by a careful study of which it will 
be possible to select such acids as are most likely to be present 
in the unknown solution under investigation, and also to neglect 
a number of acids which, from the solubility of their salts, 
together with the character of the solution (acid, alkaline, 
neutral and aqueous, or otherwise), will necessarily be absent. 



TABLE SHOWING THE SOLUBILITY OF SALTS. 



Acetate 

Arsenate .... 

Arsenite 

Borate 

Bromid 

Carbonate . . . 

Chlorate 

Chlorid 

Chromate. . . 

Cyanid 

Iodid 

Nitrate 

Oxalate 

Oxid 

Phosphate . . . 

Silicate 

Sulphate. . . . 

Sulphid 

Sulphocvanat 
Tartrate 



K 


Na 


NH 4 


Mg 


Ba 


Sr 


Ca 


Mn 


Zn 


Co 


Ni 


Fe 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 


w 


a 


wa 


wa 


a 


a 




a 


a 


a 


w 


w 


w 


wa 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


a 


wa 


wa 


w 


w 


a 


a 




w 


w 


w 


w 


wa 


w 


w 


a 


a 


ai 


ai 


ai 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 




a 


w 


w 


w 


a 


a 


a 


a 


a 


w 


w 


w 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 




a 


a 


a 


a 


a 


a 


a 


a 


a 


w 


w 


w 


w 


1 


1 


Wl 


w 


w 


w 


w 


w 


w 


w 


w 


wa 


w 


w 


w 


a 


a 


a 


a 


a 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


w 


wa 


a 


a 


a 


wa 


a 


w 


a 


wa 



85 



86 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



TABLE SHOWING THE SOLUBILITY OF SALTS.— CONCLUDED 



Cd 



Acetate 

Arsenate 

Arsenite 

Borate 

Bromid 

Carbonate 

Chlorate 

Chlorid 

Chromate. . . . 

Cyanid 

Io'did 

Nitrate 

Oxalate 

Oxid 

Phosphate 

Silicate 

Sulphate 

Sulphid 

Sulphocyanate 
Tartrate 



Cr 2 


Al 2 


Sb 


Sn" 


Sn lv 


Au 


Ag 


Hg 2 


Hg 


Pb 


Bi 


Cu 


w 


w 


w 


w 


w 




wa 


wa 


w 


w 


w 


w 


a 


a 


a 


a 


a 




a 


a 


a 


a 


a 


a 






a 


a 


a 




a 


a 


a 


a 




a 


a 


a 




a 






a 






a 


a 


a 


w 


w 


wa 


w 


w 


w 


i 


ai 


wa 


Wl 


wa 


w 














a 


a 


a 


a 


a 


a 


w 


w 




w 






w 


w 


w 


w 


w 


w 


w&i 


w 


wa 


w 


w 


w 


i 


ai 


w 


Wl 


wa 


w 


a 




a 


a 






a 


a 


wa 


ai 


a 


w 


a 










w 


1 




w 


a 


wa 


a 


w 


w 


wa 


w 


w 


a 


1 


a 


a 


wa 


a 


a 


w 


w 




a 


a 




w 


w 


w 


w 


a 


w 


w 


a 


a 


a 


w 




a 


a 


a 


a 


a 


a 


a&i 


a&i 


a 


a 


a&i 




a 


a 


a 


a 


a 


a 


a 


a 


a 


a 


a 




a 


a 


a 


a 


a 


a 


a 


ai 
















a 




a 


w&a 


w 


a 


w 


w 




wa 


wa 


wa 


l 


a 


w 






a 


a 


a 


a 


a 


a 


a 


a 


a 


a 


w 








w 




l 


a 


w 


a 




a 


w 


w 


w 


wa 






a 


a 


a 


a 


a 


wa 



w," soluble in water; a, insoluble in water, soluble in acids; i, insoluble in water or acids; wa, 
sparingly soluble in water, readily soluble in acids; wi, sparingly soluble in water and acids; ai, 
sparingly soluble in acids only. 

In this connection it is well to remember that practically all 
nitrates and chlorates are soluble in water; sulphates are mostly 
soluble, except those of barium, strontium, and calcium. Phos- 
phates (di- or trimetallic) , silicates, oxalates, and borates are 
practically insoluble, except those of the alkaline metals. This 
latter statement is also true of carbonates, except that some of 
the carbonates will dissolve to an appreciable extent in water 
containing C0 2 . Chlorids, bromids, and iodids are nearly all 
soluble except those of the first-group metals. Sulphids are 
insoluble except those of Groups V and VI. Acid salts are 
usually more soluble than neutral salts. 

In making qualitative tests for the acids it is not necessary 
to separate them one from the other, as it is in the case of metals ; 
hence the tests are individual ones, usually made upon the origi- 
nal substance or solution, and often require confirmation before 
conclusive evidence is obtained. The grouping is, therefore, 
simply for convenience, as it thus becomes possible to exclude a 
considerable number of acids by a single general test. 



ANALYTICAL REACTIONS OF THE ACIDS 87 

Acid Groups. 

Group I may include such acids as give effervescence when 
their dry salts are treated with dilute H 2 S0 4 , as H 2 C0 3 , H 2 S, 
H2S2O3, H 2 S0 3 and HCN. 

Group II may include acids giving a precipitate with AgN0 3 
in dilute HNO3 solution, as HC1, HBr, HI, HCN, HCNS, HN0 2 , 
HCIO, H 4 FeCy 6 , H 3 FeCy 6 , H 2 S 2 3 , H 2 S and HPH 2 2 . 

This second group may be further subdivided into three parts 
according to the color of the precipitate obtained (pages 89 and 91). 

Group III may include acids forming insoluble salts with 
BaCl 2 or CaCl 2 and not found in Groups I or II, or H 2 S0 4 , H 2 C 2 4 , 
H 3 P0 4 , H 3 B0 3 , H 2 Cr0 4 and H 2 Si0 3 . 

. Besides the acids found in these groups there are three 
others of common occurrence: nitric (nitrates), chloric (chlo- 
rates), and acetic (acetates). 

Detection of Acids of Group I. 

(Acids effervescing with dilute sulphuric acid. H2CO3, H 2 S, H2SO3, H2S2O3, 

HCN.) 

To a test-tube a quarter full of the unknown solution, or a little 
dry substance on a watch-glass, add dilute H 2 S0 4 . If solution is 
very dilute, concentrate it before making test, as a slight amount 
of gas might be absorbed by the water. Watch carefully for 
any escape of gas and note any odor which may be given off. 

Carbonates evolve C0 2 , odorless, but if passed into lime-water 
or baryta-water will give white precipitate of CaC0 3 or BaC0 3 . 

Sulphids evolve H 2 S, odor of rotten eggs. Confirm by 
adding a little dilute H 2 S0 4 to the suspected powder (or solu- 
tion) in a test-tube and holding over the mouth of the tube a 
piece of filter-paper wet with a solution of lead acetate. The 
test-tube may be warmed slightly to expel the gas, when a 
dark-colored stain will appear on the filter-paper, due to the 
formation of PbS. 



88 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

Sulphites evolve S0 2 , odor of burning sulphur. Sulphites 
in neutral solution may be further identified by the deep-red 
color produced with ferric chlorid. The color is discharged 
upon addition of dilute acids, HO, or H 2 S0 4 (difference from 
HCyS). 

Thiosulphates also evolve S0 2 , but at the same time the 
mixture becomes cloudy from precipitation of sulphur.* 

Thiosulphates in neutral solution treated with ferric chlorid 
give a violet to purple color, fading (rapidly upon warming) to 
a colorless solution. In mixtures of sulphites and thiosulphates 
both acids may often be detected by the use of FeCl 3 , the deep-red 
coloration of the mixed acids rapidly fading to the lighter red 
of Fe 2 (S0 3 ) 3 (not to colorless solution). 

Cyanids evolve HCN, odor of peach-stones. (Mercuric 
cyanid does not respond to this reaction.) Confirm by reactions 
given under Group II. 

Preliminary Tests for Common Acids of Groups II and III. 

(In preparatory courses the acids given in this list may be sufficient.) 

From the acids of Group II and III it may be desirable to 
select for laboratory practice, at least at the beginning of the 
acid work, the more common members of the groups. These 
will be HC1, HBr, HI, HCN, and H 2 S of Group II and H 2 S0 4 , 
H 2 C 2 4 , and H3PO4 of Group III; and tests for them may be 
made as follows: 

Chlorids give with AgN0 3 in presence of HN0 3 a white 
curdy precipitate of AgCl, much more freely soluble in ammonia 
than any other acid of the group here given except the cyanid 
AgCN, but HCN is a member of the first acid group and would 
have been previously detected. 

* Sulphids may also precipitate sulphur in presence of compounds capable of 
oxidizing the'H 2 S, such as FeCl 3 . In the absence of sulphates either H2SO3 or 
H2S2O3 can be oxidized to H 2 S0 4 by heating with HXO3 and a precipitate of BaS0 4 
obtained with BaC^. 






ANALYTICAL REACTIONS OF THE ACIDS 89 

Bromids with AgN0 3 and HN0 3 give a precipitate of AgBr 
similar in appearance to AgCl, but with a slightly yellowish 
color and only sparingly soluble in NH 4 OH. 

The tests, described on page 91, should also be made if 
bromids or iodids are suspected in the solution. 

Cyanids, see Group I. 

Sulphids will give a black precipitate with AgN0 3 , and 
have been previously considered in Group I. 

Sulphates may be detected by first acidifying the solution 
strongly with HC1 (filtering out a precipitate if any occurs) 
and adding solution of BaCl 2 ; a white precipitate will 
then be BaS0 4 , showing presence of sulphates in solution 
tested. 

Phosphates in a solution containing HN0 3 and free or 
nearly free from HC1 will give, with ammonium molybdate, 
a yellow crystalline precipitate of ammonium phosphomolyb- 
date. 

Oxalates may be detected, in a solution free from sul- 
phates and which is slightly acid with acetic acid, by simple 
addition of calcium chlorid, which will precipitate CaC 2 4 , 
white and crystalline. 

Detection of Acids of Group II. 

(Giving precipitate with AgN03 in presence of dilute HNO3.) 

To the solution to be tested add a very slight amount of 
HNO3 and a few cubic centimeters of AgNOs solution. A pre- 
cipitate indicates acids of this group. 

(a) If the precipitate is white, the presence of chlorids (HC1) , 
cyanides (HCN), sulphocyanates (HCNS), ferrocyanates 
(H 4 FeCy 6 ), hypochlorites (HCIO),* or nitrites (HN0 2 ) is in- 
dicated. 

* Precipitate is AgCl. Reaction is 3 NaCIO + 3 AgN0 3 = 2 AgCl + AgC10 3 + 
3 NaNOa. 



90 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

To separate or identify these silver precipitates allow to 
settle, decant the supernatant fluid, and add NH 4 OH. Shake 
thoroughly, when the chloride (AgCl), cyanide (AgCN), and 
nitrite (AgN0 2 ) will dissolve easily, the sulphocyanate (AgCyS) 
and the ferrocyanide (Ag 4 FeCy 6 ) slowly or slightly. 

If HCyS, or H 4 FeCy 6 is indicated, test original solution with 
a few drops of FeCl 3 . Sulphocyanates or thiocyanates (HCNS) 
give a deep blood-red solution. The color is soluble in ether 
and may be discharged by HgCl 2 . Ferrocyanids (H 4 FeCy 6 ) 
give a deep-blue precipitate. (See page 45.) 

Acids forming white silver and precipitates, easily soluble in 
ammonia, may be distinguished as follows: 

Chlorids (HC1) may be distinguished from HBr and HI 
by the ready solubility of the silver precipitate in NH 4 OH. If 
bromids and iodids are present, liberate the halogens by means 
of Mn0 2 and H 2 S0 4 and pass the mixed gases into a solution of 
anilin in acetic acid (4 c.c. of saturated aqueous solution of 
anilin and 1 c.c. glacial acetic acid). Iodin gives no precipi- 
tate, bromin gives a white one and chlorin a black one. (Prescott 
and Johnson, page 336.) 

This is a delicate and very satisfactory test for bromin but 
not so delicate for chlorin in the presence of bromids. For 
such cases the following chloro-chromic anhydrid test is recom- 
mended. Neutralize the solution if necessary, evaporate to 
dryness, transfer residue to a test-tube of rather small diam- 
eter, add a little solid K 2 Cr 2 7 , then concentrated H 2 S0 4 . De- 
cant the fumes into a wider test-tube containing a few centi- 
meters of NH 4 OH. 

If the chloro-chromic anhydrid is evolved, ammonium 
chromate will be formed. Test by making acid with acetic 
acid, then adding acetate of lead. A yellow precipitate of lead 
chromate indicates chlorin in the original solution. 

Hypochlorites liberate I from KI without the addition of 
acid. 



ANALYTICAL REACTIONS OF THE ACIDS 9 1 

Note. — Hypochlorite solutions are usually quite strongly alkaline, and in such 
cases a considerable amount of iodid is necessary to obtain the characteristic color 
in chloroform or with starch. 

Nitrites liberate I from KI after the addition of acetic 
acid. They also give a brown coloration with acetic acid and a 
crystal of ferrous sulphate. (Nitrates require a stronger acid.) 

Note. — This test is much more delicate than either of the others given, and 
if the solution is very dilute it is well to make it, even if the indigo color is not 
discharged. 

Further mix a little of the solution with a few cubic centi- 
meters of dilute indigo solution and shake. The indigo is de- 
colorized by either hypochlorites (HCIO) or by nitrites (HN0 2 ) . 

Cyanids may be tested for as under Group I. If this test is 
not conclusive, they may be converted into sulphocyanides by 
the addition of a few drops of (NH 4 ) 2 S and evaporation on the 
water-bath to dryness. It may then be dissolved in a little dis- 
tilled H 2 0, filtered and tested with FeCl 3 . 

(b) The precipitate is red-brown or orange, soluble in 
NH4OH = H 3 FeCy 6 . Ferricyanid indicated. 

(c) The precipitate is black or turns black upon warming: 
H 2 S turns black immediately. HH 2 P0 2 starts to precipitate 
white, but rapidly turns black, H 2 S 2 03 precipitates white and 
turns black slowly or upon heating. 

Sulphids (H 2 S) and thiosulphates (H 2 S 2 3 ) may also be 
detected as described under Group I, Acids. 

(d) If the precipitate, originally obtained, is yellow and in- 
soluble in NH4OH, iodids are indicated; if yellowish white and 
slowly soluble in NH 4 OH, bromids are probably present. 

Iodids and bromids (HI and HBr) may be detected in 
the same solution by adding CI water, very cautiously at first, 
and shaking with chloroform. The CI liberates the iodin, 
which is dissolved by the chloroform with violet color. Excess 
of CI decolorizes the iodin and liberates the bromin, which, in 
turn, is dissolved by the chloroform with yellow to red color. 



92 SALTS OF THE METALS AXD QUALITATIVE ANALYSIS 

Acid Group III. 

(.Acids forming insoluble barium or calcium salts, not included in the Acid 
Group I or II.) 

The members of this group may be separated from each 
other, although this is not necessary unless several members 
are present. H 2 S0 4 , H 2 C 2 4 , H 2 Cr0 4 , H 2 Si0 3 , H 3 B0 3 , H 3 P0 4 , 
separated as follows: To a little of the unknown solution add 
2 or 3 c.c. of HC1; a white or gelatinous precipitate which is not 
dissolved by dilution with water and warming is probably silicic 
acid. Make a bead test with microcosmic salt; the particles of 
Si0 2 remain undisturbed by the hot bead, forming the so-called 
silicon " skeleton. 1 ' Filter out the silicic acid and add CaCl 2 
or a mixture of BaCl 2 and CaCl 2 ; a white precipitate will be 
BaS0 4 * (test for sulphates). The Ba and Ca salts of all remain- 
ing acids of the group being soluble in HC1. 

Filter out the BaS0 4 , and to the filtrate add NKtOH, which 
will cause a precipitate of barium oxalate, chromate, borate, and 
phosphate. Filter, wash precipitate two or three times, reject 
wash-water, then transfer to test-tube by making a small hole in 
point of paper and forcibly washing through with the least pos- 
sible amount of water; acidulate strongly with acetic acid, which 
will dissolve the phosphates and borates, leaving undissolved 
the oxalates (BaC 2 4 , white) and chromates (BaCr0 4 , yellow.) 



Oxalic and chromic acids as barium salts. 




Phosphoric and boric acids. 



* If the HC1 is too strong, BaCl 2 may be precipitated as such, but the pre- 
cipitate in this case will form more slowly than the BaS0 4 ; it will have a crys- 
talline appearance and will dissolve upon addition of water. 



ANALYTICAL REACTIONS OF THE ACIDS 93 

Divide the filtrate into two parts, (a) and (b). Test one 
part, (a), for H 3 P0 4 by adding to it an excess of ammonium 
molybdate* (in HN0 3 ), when a yellow precipitate (forming 
sometimes after several hours' standing) is ammonium phospho- 
molybdate (test for phosphates); the mixture may be warmed 
to hasten precipitation; the degree of heat should not exceed 
40 C.j as the ammonium molybdate might be decomposed, 
giving a yellow precipitate similar to the phosphomolybdate. 

Note. — If As is present, it must be removed by H2S before testing for H3PO4. 

Test the other part, (&), for H3BO3 by evaporating to dryness 
in a porcelain dish; then moisten with strong H 2 S0 4 , cover with 
a little alcohol, and ignite. Boric acid will give to the flame 
(particularly the edge) of the burning alcohol a green color due 
to formation of ethyl borate. This color is more easily apparent 
if the dish is placed in a darkened corner. 

A test for H3BO3 may also be made with turmeric paper, 
which if dipped into a solution of boric acid, or of a borate mixed 
with HC1 or H 2 S0 4 to slight but distinct acid reaction, and dried 
at ioo°, becomes red; the red color becomes bluish black or 
greenish black when moistened with a solution of an alkali or 
an alkaline carbonate. If there is a suspicion that H 2 Cr0 4 and 
H2C2O4 are both present, dissolve the precipitate of barium 
oxalate and chromate off the paper with dilute HC1; divide the 
nitrate into two parts and test one for H 2 Cr0 4 by addition of 
H 2 2 , which with chromates in presence of HC1 produces a deep- 
blue solution and ultimately CrCl 3 . 

In the absence of chromates, the precipitate being white, 
oxalates may be confirmed by coloring the second part of the 
solution a faint pink with a dilute solution of KMn0 4 and warm- 
ing, when the color will be discharged. 

In the presence of chromates, the precipitate being yellow, 
it will be necessary to test the original solution for oxalates 

* Preparation of ammonium molybdate solution, appendix p. 377. 



94 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 

as follows: To a few centimeters of the unknown add alcohol; 
warm. The chromate will be reduced to CrCl 3 . Add NH 4 OH 
till alkaline and filter out the precipitate, Cr(OH) 3 . The 
filtrate may be tested for oxalic acid as above, or with CaCl 2 ; 
a white precipitate being CaC204. 

Acids of Group IV. 

The remaining acids of importance not included in either 
of the three preceding groups are nitric, HN0 3 , chloric, HC10 3 , 
and acetic, HC 2 H 3 2 . 

Nitrates. — Saturate 5 c.c. of a very dilute nitrate solution 
with FeS0 4 . Filter and carefully underlay the clear filtrate 
with concentrated sulphuric acid; a dark ring (pale red-brown 
to nearly black) at point of contact of the two liquids shows 
presence of a nitrate. 

Chlorates. — A solution free from chlorids or hypochlorites 
treated with Zn and dilute H 2 S0 4 will give a test for HC1 if 
chlorates were originally present, the chlorate having been re- 
duced by the nascent H : 

2 KC10 3 + 6 Zn + 7 H 2 S0 4 = 6 ZnS0 4 + K 2 S0 4 + 2 HC1 + 6 H 2 0. 

Boiling with sulphurous acid also reduces HC10 3 (and HCIO) 
to HC1. 

If the substance is in solid form, a very small particle may 
be warmed with concentrated H 2 S0 4 . Chlorates detonate and 
give off yellow fumes of C10 2 : 

3 KC10 3 + 2 H 2 S0 4 = 2 KHS0 4 + KC10 4 + 2 C10 2 + H 2 0. 

Acetates give with ferric chlorid a red color which is not 
discharged by HgCl 2 (difference from sulphocyanate) , but may 
be discharged by HC1 (difference from sulphocyanate and 
meconate) . 

A more positive test is the formation of the ethyl ester 



ANALYTICAL REACTIONS OF THE ACIDS 95 

or acetic ether. A blank test for comparison should always 
be made, the method of procedure being as follows : 

Take two test-tubes of practically equal diameter, mix in 
each equal volumes of alcohol and strong H 2 S0 4 ; warm the tubes 
together; then into one introduce a few centimeters of the un- 
known solution, and into the other an equal volume of H 2 0. 
Heat again to a boiling-point and compare the odors from the 
two tubes. The acetate is easily detected if present. 

Laboratory Exercises XXIV and XXV. 
Unknown Solutions Containing Acids and Bases of Group VI. 



CHAPTER X. 
ANALYSIS IN THE DRY WAY. 

In the examination of solid substances much may be learned 
by a few simple tests directly applied to the substance, which 
has been reduced (if necessary) to the form of a powder. 

Some of these are usually used as preliminary to the solu- 
tion of the substance and regular analysis in the wet way. These 
tests may be made quickly, and, with a little elaboration, will 
often give all the information required regarding an unknown 
substance. 

The practical questions of actual experience are usually 
simple ones. It is not an analysis of an unknown solution 
possibly containing all the metals of one or more groups that 
interests an active practitioner, but a specific inquiry as to 
whether or not this or that preparation contains or does not 
contain the necessary or the undesirable ingredient, whether 
the thing is of the composition or of the strength represented, 
and a few minutes' work in the laboratory, especially if aided 
by the microscopical tests given in a subsequent chapter, will 
frequently be found sufficient to answer questions of this 
character. 

The tests made in the dry way are not as delicate, nor are 
the results obtained (especially negative ones) as conclusive, as 
those of a systematic analysis of the substance in solution, and 
in occasional cases it may be necessary to resort to the more 
tedious process. 

Before undertaking the analysis of a substance, note care- 
fully its physical properties of odor, color, and solubility; also 
whether it is magnetic, metallic, or crystalline. 

9 6 



ANALYSIS IN THE DRY WAY 97 

The volatile acids, certain ammonium compounds, bromin, 
and iodin may be detected frequently by their odor. 

Colors of Salts and Solutions. 
The following colored salts are soluble in water : 

Black Silver albuminate (argyrol, etc.). 

Violet or purple Chromic salts and permanganates. 

Cr0 3 and acid chromates, K 3 FeCy6, sodium- 



nitro-prusside, H 2 PtCl 6 . 

Reddish brown or purple-red Manganic salts. 

Reddish yellow Ferric salts and AuCl 3 . 

, r „ ( Neutral chromates of the alkalies, salts of 

Yellow < 

( uranium. 

Pale yellow K 4 FeCy 6 (Potassium ferrocyanide). 

Pink Salts of cobalt. 

Pale pink Manganous salts. 

( Ferrous salts, nickel salts, certain copper 

( salts. 

Dark green Some chromic salts. 

Blue-green Chromates. 

Blue Cupric salts. 

The following colored substances are insoluble in water: 

r Carbon and carbids, metals, many metallic 
Black < sulphids, oxids of Cu, Fe, Mn, and Pb. 

' Iodin is bluish black. 

Red HgO, HgS, Hgl 2 , Pb 3 4 , As 2 S 2 . 

Brick-red Amorphous phosphorus, Fe 2 03. 

Light brown PbO (litharge). 

r S, HgO, CdS, As 2 S 3 , Pbl 2 , Ag 3 P0 4 , ammo- 
Yellow < nium phospho-molybdate, and chromates 

( of the heavy metals, PbCr0 4 , BaCr0 4 . 
P ( Some copper compounds, Cu 2 I 2 , Paris green, 

r6en I etc., Cr 2 3 . 

p, ( Some copper compounds, Prussian blue, 

ultramarine; anhydrous salts of cobalt. 



98 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



METHODS OF EXAMINATION. 

Powder the substance and apply tests described in 
chapter, which will be considered in the following order: 

A. Ignition with free access of air. 

B. Closed- tube test. 

C. Flame test on platinum wire. 

D. Examination with the blow-pipe on plaster slab. 

E. Bead tests on platinum wire. 

F. Special tests, distinguishing or confirmatory. 



this 



A. Ignition in Air. 

This test may be made on a crucible cover or on platinum 
foil. If there is any probability of I, Br, CI, P or easily reduced 
metallic compounds in the unknown substance, the platinum 
foil is likely to be destroyed ; hence, the porcelain is recommended. 

The heat employed should be very low at first; then it 
should be gradually increased and the test carefully watched. 

The majority of phenomena occurring under A are more 
easily observed in the test made with the closed tube, B, and 
will be given under 'that head. 

Observed Phenomena. Indications. 



The substance melts and steam is given off. 



The substance burns (a) at comparatively low 
temperature with blue flame and odor of 
S0 2 or burning matches. 

(b) With yellow flame and much smoke. 

(c) Blackens and then burns at fairly high 

temperature, leaving white or gray ash. 

(d) Blackens without burning. 

Vapors are given off: 

(a) Of a violet color. 

(b) Of a red-brown color. 

(c) Of a greenish-yellow color. 

(d) White, practically odorless. 



Water of crystallization, 
NH 4 N0 3 orH 2 C 2 04, which 
entirely disappear. 

Sulphur. 



Fat, waxes, resins, etc. 
Carbonaceous matter other 

than fats, etc. 
Formation of oxids of Fe, 

Co, Ni, or Cu. 

Iodin. 

Br or nitrogen oxids. 
Chlorin or C10 2 . 
Some ammonium salts, 
NH 4 C1, (NHO2SO4, etc. 



ANALYSIS IN THE DRY WAY 



99 



Observed Phenomena. 

(e) White with odor of NH 3 . 
(J) White with odor of garlic. 
(g) White and yellow with ammoniacal or 
empyreumatic odor. 
The substance decrepitates. 

Examine residue on foil (porcelain) ; add a drop 
or two of water and test with litmus-paper. 
If found to be acid. 
If alkaline without blackening. 

If alkaline with blackening. 



Add a drop of dilute HC1, effervescence. 



Indications. 

Ammonium carbonate. 

Arsenic. 

Organic matter. 

Water held mechanically by 
crystals, as NaCl, etc. 



Acid salts. 

Fixed alkali hydrates or 
carbonates. 

Carbonate formed by com- 
bustion of organic com- 
pounds. 

Carbonates. 



B. Closed-tube Test. 

Select a tube of soft glass about 5 or 6 inches in length. 
Seal one end and enlarge slightly. Into the bulb thus formed 
introduce a few grains of the unknown powdered substance. 
Heat carefully, making the following tests at various stages of 
the process. Note the odor of escaping gases. 

Test for oxygen by inserting a glowing splinter into the tube. 

Test for combustible gases by occasionally applying flame 
to the open end of the tube. 

Bring to the mouth of the tube a clear drop of Ba(OH) 2 
solution. If the drop becomes turbid, C0 2 is indicated. 



Observed Phenomena. 

Steam condenses in cold part of tube. 
Oxygen is evolved. 



Carbon Dioxid is evolved. 



A Combustible Gas is formed: 

(a) Burning with a luminous flame, black 

residue remains in tube. 
(&) Burning with a blue flame. 
(c) Burning as in (b) and with odor of SO2. 
A Sublimate forms in the cooler part of the 
tube. Examine under microscope. 



Indications. 

See under A. 

A peroxid, chlorate, some 
oxids (as HgO), alkali ni- 
trates. 

Carbonates, oxalates (at 
high temperature), or- 
ganic matter. 

Hydrocarbons from organic 

matter. 
CO from oxalates. 
H 2 S from moist sulphids. 



IOO SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Observed Phenomena. 

Colorless with partial decomposition. 

Color is white with production of garlic odor, 
crystalline. 

Color is white when cold. Yellow when hot, 
crystalline. 

Color is white — it sublimes directly with- 
out melting and blackens with NH 4 OH. 

A white sublimate which by treatment with 
slaked lime yields NH 3 . 

A white sublimate of As 2 3 with black 
residue in tube and odor of acetic acid. 

Sublimate is gray, consisting of small glob- 
ules which can be made to unite by rub- 
bing. 

Sublimate consists of reddish yellow to red 
globules, yellow when cold. 

Sublimate darker than above and reddish 
yellow when cold. 

Sublimate is brown to black " metallic mir- 
ror," soluble in NaClO. 

Ditto; dead black, insoluble in NaClO. 

Sublimate is black accompanied by violet 
vapor. 

Sublimate black, turning red when rubbed. 
No sublimate is formed, but the color 
changes to 

Yellow when hot, white when cold. 

Reddish brown when hot, yellow when cold. 

Black when hot, red when cold. 

Black when hot, brick-red when cold. 

Dark orange when hot, yellow when cold. 
Black residue without other visible mani- 
festation. 
Substance melts without a sublimate being 
formed. 



Indications. 

Oxalic acid. Plate i, Fig. i. 
As 2 3 . Plate i, Fig. 2. 

HgCl 2 . Plate 1, Fig. 3. 

HgCl. 

Ammonium salts. Plate 1, 

Fig. 4. 
Paris green. 

Hg from HgO, amalgam, 
etc. Plate 1, Fig. 5. 

Sulphur. 

Native sulphid of arsenic. 

Metallic arsenic. 

Metallic antimony. 
Iodin. Plate 1, Fig. 6. 

HgS, cinnabar. 



ZnO. 

PbO or Bi 2 3 . (See D.) 

HgO (Hg sublimes). 

Fe 2 3 . 

Chromates of Pb, etc. 

Oxids of Cu, Co, etc. (See 

A.) 
Salts of the alkaline metals. 



C. Flame Test with Platinum Wire. 



Introduce the substance on platinum wire into the edge 
of the flame. More satisfactory results are sometimes obtained 
if the solid is first moistened with HC1 (page 71, note). The 
flame is colored as follows : by Na, yellow; K, violet; Li, carmine; 
Sr, crimson; Ca, orange-red; Ba, yellowish green; Cu, usually 



bright green; Q1CI2, an intense blue: 
greenish blue; Pb, As, Bi, livid blue. 



H3BO3, pale green; Sb, 



PLATE I. — SUBLIMATES. 




Fig. i. 
Oxalic Acid (Sublimed). 




Fig. 3. 
Mercuric Chlorid (Sublimed). 





Fig. 2. 
Arsenic Trioxid. 




Fig. 4. 
Ammonium Sulphate (Sublimed). 



Fig. 5. 
Mercury from HgO. 




ANALYSIS IN THE DRY WAY 



IOI 



D. Blowpipe Test on Plaster.* 

Smooth plaster slabs about i inch wide and 4 inches long are 
well suited for these tests. These may be prepared by making 
a magma of calcined plaster and pouring upon a glass plate. 
Before it hardens mark deeply with a spatula into slabs of 
desired shape and, after it is thoroughly dried, break as marked. 

Make a little depression near one end of the slab and in it 
place a small amount of the substance to be tested; then if 
a fine oxidizing flame is made to play over the surface of the 
assay, characteristic coatings of oxid or sublimate may be 
obtained. 

In many cases the character of the substance may be deter- 
mined more easily by first moistening the assay with various 
reagents. Tetrachlorid of tin, cobalt nitrate, and "sulphur 
iodid" are the most valuable of the reagents so used. The 
" sulphur iodid" is not of definite composition, but a mixture 
of about equal weights of sulphur and potassium iodid. 



D. I. Examination without Reagents. 
Observed Phenomena. Indications. 



Substance melts to bright metallic globules 
with brownish-yellow deposit near assay. 
Requires high heat. Assay revolves. 

Substance melts to bright globule with coat- 
ing on plaster, deep orange when hot, light 
yellow when cold. 

Substance remains or becomes black without 
melting. No coating on plaster. 

Substance volatilizes with white fumes, but 
leaves dark stain; gray to black. 

Substance melts with white or gray oxid on 
assay. 

Forms a white or gray oxid without fusion. 
Coating on plaster is yellow over brownish 
black. 



Silver. 



Lead or bismuth (See D. II.) 



Copper cr iron. (See A; 

also F.) 
Antimony or arsenic. See 

F.) 
Tin. (See D. III.) 

Cadmium. 



* Substances sufficiently identified by previous tests have been omitted. This 
method will be found useful mainly in the identification of metals. 

The Author was greatly aided in the preparation of this list by Mr. Geo. F. S. 
Pearce of the Harvard Dental School, who carefully verified each test. 



102 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



Observed Phenomena. 

Forms bulky white oxid with active combus- 
tion of assay. 
Forms gray coating easily volatilized. 

Cherry-red — crimson to black according to 
amount of substance deposited. Odor of 
rotten horse-radish; coating not permanent. 

White coating or white fumes at very high 
heat. Assay burns with bluish-white light. 

Silver-white. Assay remains unchanged. 



Indications. 

Magnesium. 

Mercury from amalgams. 

(See D. II.) 
Selenium. 

Zinc. (See D. III.) 
Platinum, metallic. 



D. II. Cover Substance with KI and S. Use Oxidizing Flame. 



Observed Phenomena. 

Dirty- white and light-gray coating. Treated 
with fumes of strong NH 3 and again placed 
in oxidizing flame gives bright-red color. 
Metallic globule is dull and brittle. 

Dirty white half an inch from assay. Brown 
directly under assay. No change when 
treated as above with strong ammonia 
fumes. Metallic globule is bright and 
malleable. 

No coating near assay. Lead-colored, one to 
one and a half inches, shading to yellow. 

Coating bright red when hot, fading to yellow 
when cold. 

Fine brown coating, very volatile. 



Indications. 



Bismuth. 
Lead. 

Mercury. 

Cadmium. 

Antimony. 



D. III. Examination with Solution of Cobalt Nitrate. 

Heat substance on plaster in the oxidizing flame, moisten 
well with cobalt nitrate, and again apply oxidizing flame. 



Observed Phenomena. 

Color is deep blue. 

Substance is infusible. 

Color is fine blue. Substance fusible. 

Color is yellowish green. 
Drab to bluish green. 



Indications. 

Aluminium. 

Infusible silicates. (SeeF.) 

Alkaline silicate, borate, or 

phosphate. 
Zinc. 
Tin. 



ANALYSIS IN THE DRY WAY 



103 



D. IV. Examination with Tetrachlorid of Tin. 



Observed Phenomena. 

Coating pale blue to lavender. 
Coating fine blue, in places almost black. 
Delicate pink to red produced only by oxidiz- 
ing flame. 



Indications. 

Bismuth. 

Antimony. 

Neutral and acid chromates. 



E. Bead Tests. 

The bead tests are made with borax, as described on page 5 1 , 
or in a similar manner with microscosmic salt, NaNH 4 HP0 4 , 
which by action of the heat gives up NH 3 and H 2 0, becoming 
sodium metaphosphate, NaP0 3 . These substances fused on a 
loop of platinum wire unite with many of the metallic oxids, 
forming " beads" of various characteristic colors, some of the 
more important being given below. 

With Borax. 

Co in the oxidizing flame gives an intense blue bead. 

Ni gives a red-brown, yellow when cold. 

Cu gives a green, blue, or bluish green when cold. 

Cr gives green. 

Fe gives a red, yellowish when cold. 

Mn gives an amethyst. 



With Microcosmic Salt. 

Cobalt, copper, nickel, and iron give colors similar to those 
obtained with borax. Manganese gives a violet bead when 
heated in the oxidizing flame, but a colorless one in the reducing 
flame. 

F. Special Tests Distinctive or Confirmatory. 

The oxids of copper and iron may be distinguished by 
adding a drop of HN0 3 , warming gently to drive off excess 



104 SALTS OF THE METALS AND QUALITATIVE ANALYSIS 



of acid (high heat will decompose the nitrate, giving the oxid 
again), and then adding a drop of solution of K 4 FeCy 6 . Fe 
will give a dark-blue coloration; Cu will give a brown. 

To distinguish between As and Sb stains, add a drop of 
hypochlorite solution (NaCIO). The arsenic stain will dis- 
solve; the antimony stain will remain unaffected (see page 33). 

Antimony gives a very characteristic coating on plaster if 
treated with tetrachlorid of tin. The coating is bluish black 
near assay, fading away to a very delicate color at greater 
distance. It appears almost immediately and is permanent. 

In case of suspected silicates make the "silica skeleton" with 
a bead of microcosmic salt (page 92). 






Laboratory Exercise XXVI. 
Preliminary tests with metals and solids other than salts. 



Laboratory Exercises XXVII and XXVIII. 

Identification of unknown metals and analysis of solid sub- 
stances. 



PART II. 

DENTAL METALLURGY. 

INCLUDING THE CHEMISTRY OF ALLOYS, AMALGAMS, 
SOLDERS, AND CEMENTS. 

CHAPTER XL 
THE METALS. 

Properties of the Metals. 

Metals are malleable in order as follows from gold, the most 
malleable, to nickel, the least: Au, Ag, Al, Sn, Cu, Pt, Pb, Cd, 
Zn, Fe, Ni. 

Metals are ductile from most to least as follows : Au, Ag, Pt, 
Fe, Ni, Cu, Cd, Al, Zn, Sn, Pb. 

Metals conduct heat and electricity in the same order until 
Sn is reached. From Sn the order given is correct for heat 
but not for electricity: Ag, Cu, Au, Al, Zn, Cd, Sn, Fe, Pb, 
Pt, Bi. 

The melting-point of the various metals is of considerable 
importance in the preparation of alloys. The following table 
has been compiled from the latest available results. The de- 
grees given are according to the centigrade scale: 

Pt 2000 Cu 1054 Zn 420 (bums) 

Ni 1450 Ag 954 Pb 326 

Cast steel 1375 Al 700 Cd 320 

Cast iron 1275° Mg 500 (burns) Bi 268 

Au 1075 Sb 432 Sn 238 

105 



io6 



DENTAL METALLURGY 



The expansion of the various metals under the influence of 
heat is fairly constant and there have been determined co- 
efficients of expansion. These represent the amount of linear 
expansion of the metals due to a rise in temperature of i° C, 
usually from o° to i°. The coefficients are not absolutely con- 
stant, and the amount of expansion observed between o° and i° 
may differ somewhat from that between 50 and 51 . The 
coefficients vary widely for the different metals; for instance, 
in passing from o° to ioo° mercury expands 1/16 of its linear 
measure, copper 1/598, and platinum 1/1123. 

Hall's Dental Chemistry gives the following table of expan- 
sion from cadmium to platinum: 

Cd 1/326 Ag 1/518 Ni 1/787 

Pb 1/342 Cu 1/598 Fe (cast) 1/934 

Zn 1/343 Bi 1/617 Sb 1/952 

Al 1/432 Au 1/689 p t 1/1123 

Sn 1/448 

The only other general property of the metals directly 
affecting their use in dental practice is the electric or galvanic, 
that is, the electropositive or negative relations they sustain to 
one another. 

The metals are electropositive to each other in the fol- 
lowing order from zinc, the most positive, to platinum, the least : 
Zn, Cd, Sn, Pb, Fe, Ni, Bi, Sb, Cu, Ag, Au, Pt; 
and C is negative to all. 

Thus if a battery is constructed with Zn as 
represented in the cut (Fig. 5), and iron in place 
of the carbon, then the iron will be electroneg- 
ative to the zinc, and hydrogen will be evolved 
from its surface; if, on the other hand, Fe is used 
in place of the zinc, and the carbon remains as in 
the cut, the Fe will be electropositive to the 
carbon, and oxygen will be evolved from its 
surface. This property of metals has a direct bearing upon 




Fig. 5. 



THE METALS 107 

dental science, because human saliva may be an exciting fluid 
for the generation of galvanic currents, its activity being in- 
creased by an abnormal reaction either acid or strongly alkaline, 
and it is only necessary to place in the mouth properly related 
metals, as amalgam fillings or otherwise, to produce the elements 
of a galvanic battery. 

The currents thus generated are, of course, infinitesimal, but 
they are constant and may aid in the disintegration of fillings 
and in the solution of the constituent metals. Regarding the 
extent to which electric currents may exist in the mouth, see 
Miller's Micro-organisms of the Human Mouth. 



CHAPTER XII. 

ALLOYS. 

An intimate union of two or more metals, usually produced 
by fusion, forms an alloy. Such a union of one or more metals 
with mercury is an amalgam. 

An alloy designed to be used in the preparation of dental 
amalgams is known as an amalgam alloy. 

Some metals can be fused together in all proportions, as 
Pb and Ag. Others can be made to unite only in limited pro- 
portions, as Pb and Zn. Lead will carry only 1.6% of zinc, 
while zinc will unite with only 1.2% of Pb. Excess in either 
case separates out. 

The properties of an alloy are, as a rule, the modified proper- 
ties of its constituent metals. An exception to this rule might 
be made of the sonorous quality of bell-metal and like alloys, 
this being hardly a property of the constituent metals at all. 

Following are some of the~ more common alloys. The pro- 
portions given are general formulae and may, as a rule, be varied 
considerably: 

Aluminium bronze, yellow, resembles gold, Cu 92, Al 8. 
Bell-metal, Cu 80, Sn 20. 
Brass, Zn 1, Cu 2. 
Britanniametal, Cu 2, Sn 82, Sb 16. 

Bronze, Cu 65 to 84, Zn from 31.5 to 11, Sn from 2.5 to 4. 
Coin silver, Ag 90, Cu 10. 
Dental alloys, see page 117. 
Dental gold, Cu 85, Zn 15. 
German silver, Cu 50, Ni 30, Zn 20. 

108 






ALLOYS 109 

Composition of different samples of German silver may differ 
widely; some contain about 2.5% of iron and the amount of 
Cu may vary from 40 to 60%. 

Gun metal, Sn 11, Cu 100. 

Solder, see page 127. 

Sterling silver must contain 92.5% Ag. 

Type metal, Pb 78, Sb 15, Bi 7. 

All alloys (excluding amalgams) are solid at ordinary tem- 
peratures with one exception; this one is an alloy of one part 
potassium with three parts sodium. 

The melting-point of an alloy is often lower than that of the 
metals entering into its composition and usually lower than 
the mean melting-point of its constituents. 

In making alloys the tendency to separation of the several 
metals is greater if the alloy is allowed to cool slowly; hence 
three essentials in the process are: Complete fusion, which 
makes possible thorough mixing, and after this has been attained 
rapid cooling. As the fused mass is to be cooled as quickly 
as possible after fusion is complete, it is desirable to use the 
least amount of heat practicable in effecting the desired result. 
To this end fuse first the metal with the lowest melting-point, 
then add other metals in the order of their melting-points. 
The more difficultly fusible metal will in a sense dissolve in 
the more easily fusible metal; an alloy is formed and its tem- 
perature has been kept far below the melting-point of the high 
fusing constituent. This general rule, however, may be modified 
by the proportion of metal used; thus, in making a silver- tin 
amalgam-alloy containing 60% of silver it is better first to melt 
the silver under a flux of carbonate of sodium or borax to prevent 
superficial oxidation, then add the tin, and lastly any other 
metal to be used. The mixing is attained by stirring with a 
wooden stick and the cooling by turning quickly into a cold clean 
mold. For class work or in making small amounts (20 grams) 
of alloy, the Fletcher melting arrangement shown in Fig. 6 is 




HO DENTAL METALLURGY 

very convenient. The metals are melted in the graphite crucible 
and then by tipping up the whole contrivance the melted metals 
flow back into the ingot mold. If the alloy is to be used in the 
preparation of dental amalgams it must be reduced 
to fine turnings or filings suitable for ready amal- 
gamation. This is best accomplished in the lab- 
oratory by means of a coarse file, the ingot being 
held by a vise. The fine particles of iron must 
next be carefully removed with a magnet, and then 
the filings may be annealed if desired. 
The annealing of the amalgam-alloys may be accomplished 
by placing the freshly cut sample in a dry test-tube and keeping 
the test-tube in boiling water for ten or twelve minutes. It has 
been claimed that this process is one of superficial oxidation and 
the changes produced seem to be consistent with this theory. 
Again, it is claimed that the change is a molecular one of some 
sort due to change of temperature, and Prof. G. V. Black has 
shown that an alloy will anneal as rapidly in an atmosphere of 
nitrogen as of oxygen. The modification of properties produced 
by annealing varies somewhat with the composition of the alloy; 
for instance, the liability to discoloration is less in the annealed 
than in the unannealed sample, if the alloy contains Ag and Sn, 
or Ag, Sn, and Zn, but if Cu is a constituent the reverse condition 
has been found to exist. 

According to Professor Hall of Northwestern University, 
"annealed alloys take up less mercury than unannealed and yield 
upon mixing a greater quantity of dirt, which consists of a lower 
oxid of tin." The amalgam made from an annealed alloy 
works more easily than from an unannealed. 

The process of annealing up to a certain point seems to be, 
in general, beneficial; but beyond this point it may be detri- 
mental, the amalgam being less strong and more liable to shrink. 
Professor Black has shown that while it may be possible to 
stop the process of annealing at such a point that a given alloy 



ALLOYS III 

will neither shrink nor expand, it is easy to carry the process 
too far and the farther it is allowed to go the greater the shrink- 
age. It is probably true that the exact effect of annealing 
will vary with the composition of the alloy, and with different 
proportions of metals in alloys of the same general composition. 

Annealing of Gold. 

When gold-foil is heated to redness it recovers the cohesive 
property which has been lost largely by hammering. It is 
recommended that the heating be done in an electric furnace 
or on plates of mica or platinum, thus insuring uniformity of 
effect throughout the mass which it is practically impossible 
to obtain by holding the metal in the flame. See Dental 
Cosmos, Vol. XL VII, page 233. 

Non-cohesive gold, or gold in which the cohesive property 
cannot be developed by heating, may be prepared by alloying 
or treatment with carbon. Corrugated gold is of this variety 
and is prepared, according to Essig, by carbonization of unsized 
paper in intimate contact with the metal. See Essig, Dental 
Metallurgy, page 173. 

In annealing platinum a high degree of heat is required, 
but the heat should be raised gradually, and in this case also 
the electric furnace furnishes an ideal method. 

Laboratory Exercise XXIX. 
Analysis of an Unknown Alloy. 



CHAPTER XIII. 
AMALGAMS. 

In general, amalgams may be made in three different ways: 
First, by direct union of the constituents, as in the manufacture 
of sodium amalgam (page 113); second, by electrolysis of 
strong solutions of metallic salts in presence of mercury, as 
in copper amalgam (page 114), and third, by double decom- 
position as illustrated in the preparation of ammonium amal- 
gam (page 114). 

Amalgams possess the peculiar property of " setting" or 
hardening within a short time after mixing. This in some cases 
seems to be a process of crystallization, and in all cases is prob- 
ably due to molecular rearrangement of some sort. 

After an amalgam has "set" to a sufficient extent to make 
it hard to work it may be softened by application of gentle 
heat. Continued reheating is detrimental to the quality of the 
amalgam, and should be avoided; this is particularly true of 
copper amalgam. It is also possible to sometimes restore the 
plastic quality of an amalgam by adding a further slight amount 
of mercury, but the union of the second lot of Hg after the 
first has partly hardened is very unsatisfactory and results in a 
weakened product. 

Flow of Amalgams. — This property may be defined as the 
tendency to flatten or change shape under stress or pressure. 
It is common to most amalgams (copper amalgam being an 
exception, according to Dr. Black), and is possessed by many 
alloys other than amalgams. 

Tests for "flow" may be made with the "dynamometer" on 
cubes of alloy or amalgam measuring one-tenth of an inch each 
way and the results expressed in percentage of increase or de- 



AMALGAMS 



"3 



crease of one dimension. The dynamometer used for this pur- 
pose is pictured in Fig. 7 and is a modification of the apparatus 
devised by Dr. Black and described on pages 408 and 409 of the 
Dental Cosmos, Vol. 37, A- A being the molds in which the 
cubes of amalgams are set and B the point in the apparatus 
where the cube after setting is introduced with a pair of fine 
forceps. The dial is supplied with two hands, one which flies 
back the instant the cube breaks, the other remaining to indicate 
the number of pounds applied necessary to crush the cube. 
The cubes of 1/10 inch are best suited for students' practice, 




Fig. 7. 



with a dial constructed to record 250 pounds pressure. For 
accurate comparisons of thoroughly made amalgams the cubes 
must be made smaller. 

Binary amalgams, as they are sometimes called, are those 
consisting of only one metal besides mercury. These are rarely 
used in dental practice, but from them the properties of the 
amalgamated metal are most easily observed. 

Sodium amalgam may be made by direct union of the 
constituent elements. The mercury should be placed in an 
open dish under a hood, and the sodium added in small well- 
cleaned pieces. 



114 DENTAL METALLURGY 

The union is accompanied by a slight hissing noise, an eleva- 
tion of temperature and evolution of vapor carrying more or 
less mercury, hence dangerous to breathe. An amalgam con- 
taining i% sodium is a viscid liquid; if it contains 5% sodium 
it is a hard solid and intermediate percentages give varying 
degrees of firmness. Sodium amalgam, if made with arsenic-free 
Hg, is a very convenient reagent to use in making Fleitmann's 
Test (page 29). 

Ammonium amalgam has no use in dentistry, but it is of 
interest in that it is the nearest approach to which we may 
attain to the isolation of the purely hypothetical metal ammo- 
mum. It is easily made by adding sodium amalgam to a cold 
saturated solution of ammonium chlorid, thus illustrating the 
third general method of preparation of amalgams. It rapidly 
decomposes at ordinary temperature with the liberation of free 
hydrogen, ammonia-gas, and metallic mercury. The H thus 
liberated exhibits the properties of nascent H, indicating that in 
the amalgam it existed in true chemical combination, that is 
NH 4 , rather than in any physical solution. At ordinary tem- 
perature ammonium amalgam is a soft, pasty, very porous 
mass, but at much reduced temperature it becomes solid and 
crystalline, although at —39° (the freezing-point of Hg) H and 
NH 3 are still given off. 

Copper amalgam is by far the most valuable of this class 
of amalgams. It may be made by amalgamating precipitated 
copper after moistening it with nitrate of mercury (Essig). 
The precipitated Cu may be prepared by action of metallic Zn 
in a slightly acid copper sulphate solution, but must be thor- 
oughly washed with hot water to free it from zinc chlorid. The 
amalgamation may be effected by use of mortar and pestle. 
Rollins' method* by electrolysis of strong copper sulphate solu- 

* Details of this method may be found in the Boston Medical and Surgical 
Journal, February, 1886; also in Mitchell's Dental Chemistry. 



AMALGAMS 115 

tion is rather unwieldly, but illustrates very well the second 
general process for the manufacture of amalgams. 

Copper amalgam, according to Black, is absolutely rigid 
after it has once set and does not flow even to a slight extent. 
It is fine-grained and very hard. It is reduced in strength by 
reheating and does not expand or contract. In the mouth copper 
amalgam dissolves with comparative rapidity owing to the 
ready formation first of copper sulphid, then, by the oxidation of 
this compound, of the sulphate. It blackens rapidly and in con- 
sequence of the tendency to dissolve just mentioned, it may 
penetrate the dentine and thus discolor the tooth itself. 

Gold amalgam is readily made, but does not, by itself, harden 
well. An amalgam containing one part of gold to six of mer- 
cury will crystallize in four-sided prisms (Litch). 

Platinum amalgam is very smooth, is formed with diffi- 
culty unless the Pt is very finely divided, and, like gold, does not 
harden well. 

Silver amalgam, easily made but tends to expand. 

Tin amalgam, alone shrinks badly. 

Zinc amalgam, readily made, is white, but too brittle to 
be of service. 

Cadmium amalgam may be easily made at ordinary tem- 
perature, "sets quickly, and resists sufficiently, but fillings con- 
taining it gradually soften and disintegrate and may stain 
the dentine bright yellow by formation of cadmium sulphid." 
(Mitchell.) 

Effect of Various Metals in Amalgam Alloys. 

With the properties of these simpler combinations before 
us it becomes easy to understand the effect the addition of the 
various metals will have upon the properties of a silver-tin 
alloy; for practically all amalgam alloys are silver- tin alloys, 
either simple or combined with one or more other metals. 

Silver and tin are the most valuable constituents of amalgam 




Ii6 DENTAL METALLURGY 

alloys. Silver is essential to the proper setting and hardening 
of the amalgam. It tends to increase expansion and to hasten 
setting, while tin possesses the opposite characteristics. Com- 
bined with tin in the proportion of 65% silver to 35% tin, it 
forms an amalgam alloy perhaps more largely used than any 
other. It was this combination that Dr. Black succeeded in 
"annealing to zero," that is, so that upon testing it showed 
neither expansion nor contraction. 

Pure silver- tin alloys will flow from 2.5 to 10%. 

Authorities seem to agree that if a Ag-Sn alloy contains 
75% or more of silver it will expand only; while an alloy con- 
taining from 50 to 61 or 62% of silver will shrink only; and 
one containing less than 50% of silver will first shrink and then 
expand. 

The larger the proportion of tin the easier will the alloy cut,, 
but the coarser will be the filings. 

Zinc added to a silver- tin alloy tends to whiten the amalgam,, 
hastens setting, increases the flow, and, according to Essig,. 
"causes a great but slow expansion." 

Cadmium, see above. 

Antimony gives a fine grain alloy and when the Ag is less 
than 50% is supposed to control shrinkage. 

Bismuth will increase the flow of the amalgam; it is some- 
times used in low-grade Ag-Sn alloys to control shrinkage. 

Copper tends to diminish flow and gives a strength under 
pressure, sets quickly, gives better margins, and by some is 
believed to have preservative influence on the tooth substance r 
but the more copper in an alloy the more rapidly does it dis- 
color. 

Gold. — From three to seven per cent of Au in a silver- tin 
alloy diminishes shrinkage, helps the color and adds to crush- 
ing strength. The riling from such an alloy will be very fine. 

Dr. Black says 5% of gold gives a softer working property 
but retards setting of the amalgam, and makes it otherwise 



AMALGAMS 



117 



difficult to give a good finish to the filling (Dental Cosmos, 
Vol. 38, page 988). 

Platinum, according to Black, is not a desirable addition 
to a silver- tin alloy. It gives an alloy furnishing very fine filing, 
which produces a dirty working, slow-setting amalgam. 

Excess of Mercury. — In the preparation of an amalgam 
from a dental alloy it is usual to add more mercury than the 
finished product requires and then squeeze out the excess be- 
tween the fingers or otherwise. In filling a cavity, still more 
mercury is forced out, so that the composition of the deeper 
portions of a filling varies from the outer portions and probably 
accounts for the inequalities in expansion or contraction. The 
excess of Hg from the surface of a filling may be absorbed by 
a little hot gold or pure tin or by finely divided silver. 

Following is a short list of dental alloys, most of which may 
be easily prepared: 



Arington's (S. S. White's) 

*(C. A. S.) alloy, C. Ash Sons Co. 

Chase copper- amalgam alloy 

Chase's incisor alloy 

*Fellowship alloy 

Flagg's submarine alloy 

Fletcher's gold alloy (old) 

High-grade alloy (7^% gold) 

Harris's amalgam alloy 

King's occidental alloy 

*Odontographic alloy 

*Standard alloy 

Standard dental alloy (Eckfeldt) 

60% silver alloy 

Temporary alloy 

*True dentalloy. 

""Twentieth century 



Sn. Ag. Au. Cu. Zn. Sb. 



57-5 

27.16 

50 

40 

26.80 

35 

56 

4i -5 

48.1 

54-75 
26.48 

35 .03 

40.6 

40 

88 

27.13 

27.13 



42.5 
06.54 
50 
50 

67-45 

60 

40 

49 
40 

42.75 
66.87 

53-55 

52 

60 

10 

65.91 

67.03 



4 
7-5 



0.28 
8.82 
4-4 



5.02 
10 

5-73 
5 



4-9 

6. 21 
2.76 
3 



5-2i 
4.87 



0.90 



o.55 



2 
7 

2-5 
trace 



2 

i-52 
1. 10 



* Analyses by Dr. P. J. Burns of the Mass. Inst. Technology, reported in the 
Journal of the Allied Societies, June, 1908. 

The excess of mercury which has to be squeezed out of an 
amalgam carries with it more or less of the constituent metals. 



Il8 DENTAL METALLURGY 

Hall found that whatever the amount of mercury expressed, it 
carried just about 1% of tin. In the author's experience this 
amount has reached nearly i}% of tin. Silver is carried out to 
a much less extent than tin, so it is not impossible to carelessly 
make an amalgam and squeeze out enough mercury to change 
the proportion of Ag and Sn in the alloy. This change will, of 
course, be very slight, but we have seen that the contraction and 
expansion of amalgams may be affected by slight changes in 
composition. 

These formulae have been selected from various sources with 
a view to giving the student opportunity to study effects ob- 
tained by varying percentages of Sn and Ag, and by introduc- 
tion of other metals, Cu, Zn, etc. 

Tests for Amalgams. 

Color Test. — This is made upon a freshly amalgamated 
alloy, rolled into about the shape and size of a small pea, with 
a view to determine the amount of discoloration the amalgam 
is liable to undergo in the mouth. 

A ball of amalgam carefully smoothed on at least one side 
is placed for forty-eight hours in a saturated solution of hydro- 
gen sulphid, and after that time its color is compared with other 
amalgams similarly treated, or with amalgam of a similar com- 
position which has not been treated. 

Test for Expansion or Contraction. 

Black has shown that tests of this nature to be of any value 
must be made in such a way that the amount of change in the 
volume can be measured, and that the simple method of pack- 
ing glass tubes and using colored ink is wholly unreliable. 

The author uses for this purpose an apparatus similar to 
one described by Prof. Vernon J. Hall. The amalgam is packed 
closely into a "well" in a steel block, then the block is placed 



AMALGAMS 



II 9 



in the apparatus so that a counterpoised steel plunger rests on 
the column of amalgam. This plunger is operated by a very 
long needle and attached at a point so near the pivotal support 
of the needle that a rise or fall of the plunger of 1/2500 of an 
inch moves the tip of the needle, at the scale, 1/16 of an inch, 
or one degree. If the needle rises half a degree, which may 
easily be read, it would indicate an expansion of the amalgam 
of 1/5000 of an inch. 

There are two wells in each block and both of exactly the 
same depth. The figure given below will make this explanation 
easily understood, A being the steel block carrying the amalgam. 




Fig. 8. 



Test for Crushing Strength and Flow. — The test is made 
with Dr. Black's dynamometer (page 113) upon cubical blocks 
of amalgam which have been allowed to "set" for at least two 
days, and which measure 1/10 of an inch each way. 

Specific gravity may be obtained by weighing the sample 
first in water, then in air, and dividing the weight in air by 
the difference between the two weights obtained. 

It is instructive to make these tests on amalgam from alloys 
of varying composition, also on annealed and unannealed alloys 
of the same composition. 



CHAPTER XIV. 
DENTAL CEMENTS. 

Dental cements, largely used as temporary fillings and linings 
of cavities, contain oxid of zinc, oxid of copper, or rarely sulphate 
of zinc, combined, at the time the cement is used, with phosphoric 
acid or with a solution of zinc chlorid. 

There are six forms of dental cements which might be men- 
tioned: the oxyphosphate of zinc, oxyphosphate of copper, arti- 
ficial enamel, oxychlorid of zinc, oxysulphate of zinc, and tin 
cement. Of these the last three are but little used. 

Oxyphosphate of Zinc. — This is the most serviceable of 
the preparations of this class unless exception is made of the new 
artificial enamels, which have not been in use long enough to 
warrant positive assertions as to their comparative value. 

The oxyphosphate cement is usually made by adding a 
powder, consisting largely of pure oxid of zinc, colored by a 
slight amount of other metallic oxids, to a liquid consisting of 
deliquesced phosphoric acid (or a solution of phosphoric acid 
in which zinc phosphate, and possibly slight amounts of other 
phosphates, have been dissolved), till a putty-like mass results, 
which rapidly hardens and becomes capable of receiving a con- 
siderable polish. When the phosphoric acid used is the glacial 
acid, the cement may be spoken of as a metaphosphate, because 
the glacial acid, before the addition of water, and to a certain 
extent afterwards, is actually metaphosphoric acid, HP0 3 . The 
metaphosphoric acid by boiling with water or gradually by addi- 
tion of water without boiling becomes the orthophosphoric acid 
(H3PO4). 

Hall's Dental Chemistry takes the following tests from 



DENTAL CEMENTS 121 

Flagg's Plastics and Plastic Filling, as characterizing, a good 
oxyphosphate cement. 

General Tests, i. When first mixed it should yield a tough 
mass which when removed from the spatula does not adhere 
to the fingers and can be rolled into a pliable pellet. 

2. It should have a glassy surface; and, at the end of two 
or three minutes, it should rebound when dropped upon wood, 
glass, or porcelain. 

3. At the end of five minutes it should be quite hard and 
should sound like porcelain when tapped. 

4. After ten or fifteen minutes it should be dented with 
difficulty, and when broken should show a clean, sharp fracture. 

5. After twenty minutes it should be very hard, and should 
be capable of taking a good burnish. 

6. In thirty minutes it should have little or no acid taste. 

Arsenic is a frequent impurity in both zinc oxid and phos- 
phoric acid, and if present is very liable to produce an irritating 
cement, sometimes causing considerable trouble; hence, the 
material entering into the composition of any dental cement 
should be free from arsenic (see pages 28 to 31 for arsenic tests). 

The purer the zinc oxid and the phosphoric acid, from which 
the cement is made, the more durable it is found to be; so, aside 
from any question of irritation, it is quite necessary for the sake 
of the cement itself that the ingredients be pure. 

It is not intended to give the impression that the liquid should 
consist only of glacial phosphoric acid or the powder only of oxid 
of zinc. A cement thus made would set so rapidly that it would 
be of no practical value. The resulting mass would also prob- 
ably be crumbly. The powder or the liquid, one or the other, 
is usually mixed with phosphates of the heavy metals which 
would be insoluble in water, but which would dissolve in the 
strong phosphoric acid. 

A pure ZnO may be made by calcining the precipitated 
carbonate of zinc, Zn 5 (OH) 6 (C0 3 )2 + heat = 5 ZnO + 2 C0 2 + 



122 DEXTAL METALLURGY 

3 H 2 0. The heat should be below 500 F., because, if too strongly 
heated, the color suffers, becoming yellowish. 

Another method of making pure oxid of zinc is given as 
follows : Dissolve pure zinc in nitric acid, evaporate to dryness, 
and heat till fumes cease to be given off. The mechanical effect 
of the escaping oxids of nitrogen is said to leave the ZnO in the 
form of a very fine powder. 

A pure phosphoric acid can be made from the ortho-acid 
by heating till the white fumes begin to come off, then heating 
to redness, cooling and dissolving in H 2 to a thick syrup. In 
mixing cements, the powder should be worked into the liquid 
till the desired consistency is obtained. 

Oxyphosphate cement and all cements having zinc oxid for 
a base tend to dissolve in the fluids of the mouth, lactic acid and 
ammonium salts being particularly good solvents for this class 
of compounds. The addition of ferric oxid to oxyphosphate 
cement increases resistance to disintegration. One part of 
ferric oxid to 6 to 10 of zinc oxid is recommended by Rollins in 
the International Dental Journal. 

Oxychlorid of zinc is more easily soluble than oxyphos- 
phate. It shrinks more, but is credited with a preservative 
action on dentine and hence is used to some extent as a lining. 

The powder of the oxychlorid cement is ZnO with sometimes 
a little borax, or silica, or both, added. A good oxychlorid 
cement will set in fifteen or twenty minutes, but keeps on grow- 
ing harder for several hours. The following formula is recom- 
mended. 

Formula for Oxychlorid Cement. 

Oxid of zinc 10 grams, borax 0.1 gram, and powdered silica 
0.2 gram. 

Transfer to clay crucible and calcine for one-half hour in 
furnace at bright-red heat. Pulverize, sift, and bottle. The 
liquid to be used with this powder consists of 10 c.c. of pure 
HC1 saturated with pure zinc and filtered through glass wool. 



DENTAL CEMENTS 123 

Oxysulphate of Zinc. — This is used still less than the oxy- 
chlorid. It is non-irritating, dissolves easily, and is compara- 
tively soft. The following formula is taken from Hall's Dental 
Chemistry. 

Formula for Oxysulphate Cement. 

Ten grams oxid of zinc, 4 grams sulphate of zinc. Dry, mix, 
calcine for one-half hour, and sift. 

Liquid to be used with the powder may be made by dissolv- 
ing 2 grams of zinc chlorid in 10 c.c. of water. This gives a 
turbid solution and should be shaken when used. 

Oxyphosphate of copper cement (Ames's) consists of the 
usual powder and liquid. The powder contains oxids of cop- 
per, iron (slight amount), cobalt, and zinc, and, of course, is 
black in color. The liquid is phosphoric acid holding in solution 
a certain amount of phosphate of zinc. 

The cement resulting from this combination was found to 
be hard, showing practically no change of volume and resisting 
the solvent action of the saliva. 

Tin Cement. 

Dr. Arthur Scheuer, of Teplitz, Bohemia, recommends a 
preparation composed of a finely pulverized tin sponge and zinc 
oxid mixed with glacial phosphoric acid. "The powder is of a 
light-gray color, becoming slightly darker when mixed with the 
acid, but regains its original color after setting. A tin-cement 
filling can be easily inserted and when polished it has a metallic 
appearance." (Dental Cosmos, May, 1904.) 

Artificial Enamel. — Several preparations have been put on 
the market under this name, in each case with the claim that it 
makes a much harder cement and one which resists disintegra- 
tion to a much greater extent than the ordinary zinc preparations. 

The specifications of a German patent, under which one of 
these preparations is manufactured, claim that the powder con- 




124 DENTAL METALLURGY 

sists of a mixture of the oxids of beryllium and silicon, together 
with alumina and lime. The liquid consists of a 50% solution 
of orthophosphoric acid in which aluminium phosphate and zinc 
phosphate have been dissolved. 

When mixed in the usual manner these produce a cement 
which is much harder and less soluble than any of the prepara- 
tions previously considered. 

An advertisement of one of these preparations claims that 
its success is due to the use of a very valuable compound, without 
which it would be worthless, and, so far as the author has had 
opportunity to investigate this subject, this statement seems to 
be true. A qualitative analysis confirms the claim of the 
patent specifications both in regard to the composition of the 
liquid and the presence of oxid of beryllium in the powder, and 
it is probable that the value of these preparations depends 
largely upon the proportion of beryllium entering into their 
composition. 

Beryllium is a rare metal which occurs naturally with alumi- 
nium as a silicate. It forms basic compounds of such character 
as makes it suitable for use in dental cement. 

The cement powders may be tested for beryllium as fol- 
lows: Fuse a little of the powder with sodium carbonate (or 
the double sodium potassium carbonate); dissolve the fused 
mass in dilute hydrochloric acid; evaporate to dryness and 
heat to 120 C. to dehydrate the silica; take up in water with a 
little HC1 and filter; to the filtrate (probably containing Al, 
Be, Zn, and Ca) add a little ammonium chlorid, and an excess 
of ammonium carbonate, Al(OH) 3 , Be(OH) 2 , and CaC0 3 , will 
be precipitated. The beryllium, however, is easily soluble in 
the excess of (NH 4 ) 2 C0 3 . Warm (not boil) and allow to stand 
for some time to insure complete separation of Al. (Note. — 
Al(OH) 3 is much less soluble in solution of (NH 4 )2C0 3 than in 
either NH 4 OH or even NH 4 OH and NH 4 C1.) Filter. Boil the 
filtrate for a long time, when the beryllium and some zinc will 



DENTAL CEMENTS 125 

be precipitated. Filter and dissolve precipitate off paper in 
dilute HC1. To the nitrate containing BeCl 2 and ZnCl 2 add 
NH4CI in excess and NH 4 OH, which will give a precipitate of 
Be (OH) 2 . If Be and Zn only are present, the separation by 
boiling may be unnecessary. 

The liquid may be tested for dissolved phosphates by dilut- 
ing with water and adding ammonia till alkaline ; if the mixture 
remains clear, phosphates of alumina, calcium, or zinc are 
absent. Care should be used, however, in the addition of the 
ammonia, as an excess of this reagent will redissolve phosphate 
of zinc. 

If the ammonia is too strong, a precipitate of ammonium 
phosphate may be obtained, but this may be easily re-dissolved 
by the simple addition of water. 



CHAPTER XV. 
FUSIBLE METALS AND SOLDERS. 

Fusible Metals. 

Under the head of fusible alloys properly come many of 
the alloys considered on page 128 as solders. The fusible alloy 
usually contains lead or bismuth together with tin and occa- 
sionally cadmium. This may be mixed in such proportions that 
the melting-point may be anything desired down to 63 ° C. 
These alloys are largely used in the dental laboratory. Mellot's 
metal, composed of bismuth 8 parts, tin 5 parts and lead 3 
parts, is perhaps the most serviceable. This melts at about 
the temperature of boiling water. Wood's metal, melting at 
about 6 5 C, is composed of bismuth 4 parts, tin 1, lead 2, and 
cadmium 1. Rose's metal is bismuth 2 parts, tin 1, and lead 1. 
This melts at about 95 C. 

Babbitt Metal, much used in the manufacture of dies, is 
composed of copper 1 part, antimony 2, and tin 8. The for- 
mula of common Babbitt metal on the market will be found to 
differ somewhat from the above and is not so well suited for 
dental purposes. 

According to Essig's Dental Metallurgy, Dr. C. M. Rich- 
mond used a fusible alloy in crown and bridge work which he 
states is as hard as zinc and can be melted at 150 F. and 
poured into a plaster impression without generating steam. 
The formula of this alloy is as follows: Tin 20 parts, lead 19, 
cadmium 13, and bismuth 48. The following fusible-metal 
alloys are also suitable for the purpose. 



[m. 


Lead. 


Bismuth. 


Melting-point of Alloy. 


I 


2 


2 


236°F. or 113 C. 


s 


3 


3 


202 F. or 94 C. 


3 


5 


8 

126 


197 F. or 92 C. 



FUSIBLE METALS AND SOLDERS 



127 



The fusing-point of an alloy may be determined by melt- 
ing under a liquid of sufficiently high boiling-point and then 
carefully noting the temperature at which the melted alloy 
solidifies. Care must be taken that 
the temperature of the alloy is 
exactly the same as recorded by 
the thermometer. To insure this, 
in the case of an alloy with low 
melting-point, it is usually suffi- 
cient to place the alloy in water 
or brine in a test-tube which is 
immersed in a beaker of similar 
fluid, then, by raising the heat 
gradually with constant stirring 
and by taking the mean of two or 
three determinations, fairly ac- 
curate results are obtained. 

Solders. 
Solders are alloys used in join- 

- , , .. , , Fig. q. — Apparatus for Taking 

ing pieces of metal of the same Melting-Point. 

or of different kinds. One of the 

constituent metals of the alloy forming the solder is usually the 

same as the surface upon which it is to be used, hence the 

various metals require solders of special composition; for 

instance, common solder is entirely unsuited for soldering 

aluminium or gold. 

Common Solder is composed of tin and lead in different 
proportions. The larger the proportion of tin the finer is the 
solder, and the following three grades may usually be obtained: 
"Fine" or "hard" (tin two parts and lead one), "Common" or 
"medium" (tin and lead equal parts), " Coarse" or "soft" (tin 
one part and lead two parts). 




128 



DENTAL METALLURGY 



In soldering metals, it is absolutely essential that the sur- 
faces be kept clean and free from superficial coating of oxids 
which may form easily with the elevated temperature employed 
in the process. Soldering acid and the various fluxes serve this 
purpose. Soldering acid is an acid solution of zinc chlorid 
usually made by taking a few ounces of strong hydrochloric 
acid and adding zinc as long as the metal dissolves. Among 
the substances which may be used as a flux to prevent oxi- 
dation, rosin and borax are the most common. 

Soft Solders are those fusing below a red heat and include 
the common solders above mentioned, also the most fusible 
solders containing bismuth. These last are more properly 
fusible metals and are discussed under that head. 

Solders for Aluminium. — Aluminium solders with consider- 
able difficulty owing in part to the low melting-point of the 
metal, also to the fact that aluminium is attacked by alkalis, 
including borax, which makes it necessary to find some sub- 
stitute for this convenient flux. Essig recommends a flux con- 
sisting of three parts of copaiba balsam, one part of Venetian 
turpentine, and a few drops of lemon-juice. The mixture is to 
be used in the same manner as soldering acid with a solder con- 
sisting of zinc from 80 to 92 parts, aluminium from 8 to 20 
parts. Fused and finely powdered silver chlorid may also be 
used as a flux, the salt being reduced and the silver forming a 
superficial alloy. Richards recommends a solder for aluminium 
consisting of tin 29 parts, zinc 11 parts, aluminium 1 part, phos- 
phor-tin 1 part. 

Hall says that a solder which he has found very satisfactory 
may be prepared from aluminium 45 parts, tin 45, mercury 10; 
further, that the following formulae suggested by Schlosser are 
particularly adapted to soldering dental work since they resist 
the reaction of corrosive substances. 



FUSIBLE METALS AND SOLDERS 129 

Platinum-Aluminium Gold-Aluminium 

Solder. Solder. 

Gold 3 parts Gold 5 parts 

Platinum 0.1 part Copper 1 part 

Silver 2 parts Silver 1 " 

Aluminium 10 " Aluminium 2 parts 

For soldering articles of aluminium the following solder is 
given in the Pharmaceutical Era, January 10, 1895: Silver 2, 
nickel 5, aluminium 9, tin 34, and zinc 50 parts, to be used 
without flux. See also Dental Cosmos for 1906 (page 115). 

Solder for brass requires a high heat for fusion and on 
this account is known as hard solder. 

Edwinson gives the following formulae: (1) copper 13 parts, 
silver 11; (2) copper 1 part, brass 1, silver 19; (3) brass 5 parts, 
zinc 5, silver 5. The flux for brass soldering is powdered borax, 
which may be mixed with water to a paste and applied with a 
feather or a small brush. 

Solder for Gold. — Gold soldering is the most particular 
work of this class which the dentist has to do. There are a 
few requirements for a good gold solder which might be noted 
and which are also applicable to the other solders mentioned: 
(1) The color should be as nearly as possible that of the metals 
upon which it is to be used. (2) The solder should have a 
fusing-point but very slightly below that of the metal to be 
soldered. (3) The solder should flow freely. 

Litch gives the following instructions for making a zinc-gold 
solder which will have the above-mentioned properties: 

"To make the zinc-gold solder take 1 pennyweight of the 
same gold upon which it is to be used and add ij grains of zinc. 
If this is done in a crucible in the furnace, first fuse the gold 
(which should either be clean scraps or be cut from the plate; 
never use filings for this purpose), using but little borax; when 
thoroughly fused take the crucible in the tongs, drop the zinc 
into it, give the crucible a rather vigorous yet skilful shake to 
assist in mixing its contents, but without causing any to be 



130 DENTAL METALLURGY 

thrown out, and immediately pour into the previously prepared 
ingot mold. This must be done very quickly or the solder will 
require too high a heat for the fusion on account of a large pro- 
portion of the zinc being volatilized or oxidized and thus be lost 
as alloys " 

Essig gives the following formulae for alloys of gold employed 
in dentistry as solders: 

No. 1. 14 Carats Fine. No. 2. 14 Carats Fine. 

American gold coin $10.00 American gold coin . 16 dwts 

Pure silver 4 dwts. Pure copper 3 " 18 grs. 

Pure copper 2 " Pure silver 5 " 

No. 3. 14 Carats Fine. No. 4. 15 Carats Fine. 

Pure silver 2\ dwts. Gold coin 6 dwts. 

Pure copper 20 grs. Pure silver 30 grs 

Pure zinc 35 " Pure copper 20 " 

18-carat gold plate (formula Brass 10 " 

No. 11) 20 dwts. 

No. 5. 16 Carats Fine. No. 6. 16 Carats Fine. 

Pure gold 11 dwts. Pure gold 11 dwts. 12 grs 

Pure silver 3 "6 grs. Pure copper 1 dwt. 12 " 

Pure copper 2 " 6 " Pure silver 3 dwts. 

Pure zinc 12 grs. 

No. 7. 18 Carats Fine. 

Gold coin 30 parts 

Pure silver 4 " 

Pure copper 1 part 

Brass 1 " 

No. 8. 20 Carats Fine, for Crown and Bridge Work. 

American gold coin (21.6 carats fine) $10 piece 258 grs. 

Spelter solder 20.64 " 

No. 9. 20 Carats Fine, Same Use as No. 8. 

Pure gold 5 dwts. 

Pure copper 6 grs. 

Pure silver 12 " 

Spelter solder • 6 " 



FUSIBLE METALS AND SOLDERS 131 

No. 10. 20 Carats Fine, for Crown and Bridge Work. 

Zinc 15 grs. 

Pure gold 20 

Silver solder 3 " 

No. 11. Dr. C. M. Richmond's Solder for Bridge Work. 

Gold coin 5 dwts. 

Fine brass wire 1 dwt. 

No. 12. Dr. Low's Formula for Solder for Crown and Bridge 
Work, 19 Carats Fine. 

Coin gold 1 dwt. 

Copper 2 grs. 

Silver 4 " 

Solder for Platinum. — Platinum utensils may be soldered 
with any good gold solder, and a flux may be used if desired. 
When, however, the solder is used in connection with porce- 
lain work, it must be pure gold or a gold and platinum alloy. 
A 25% platinum alloy has been found to give excellent results. 
The following in regard to gold and platinum alloy is from the 
Dental Review, August, 1905: 

"The colleges and text-books tell us the proper proportions of 
gold and platinum alloys, but they usually fail to tell us how 
to do it. In most cases the platinum appears in white spots on 
the plate without producing a proper alloy. Take a small 
piece of 22-carat gold and fuse it under the blowpipe. Then 
work in all the platinum you can in small pieces until it has taken 
up all that is required. It will produce a small button of a white 
alloy which is very brittle. Add this alloy in required propor- 
tions to the gold in the crucible and it will produce a real platinum 
alloy. By this method you can make clasp gold that is pretty 
nearly as stiff as a steel spring and yet will roll and work with- 
out fracture. (Mark G. McElhinney, Ottawa, Canada.) " 

Solder for Silver. — Solder for silver usually consists of 
alloys of silver and copper with sometimes zinc and sometimes 
tin. Litch recommends a silver solder made by alloying pure 



132 DENTAL METALLURGY 

silver with one- third its weight of brass. "Brannt's Metallic 
.Alloys" give alloys of silver and copper simply. Hall recom- 
mends silver 8 parts, copper i, and zinc 2. In the preparation 
of solder containing copper, zinc, or tin, the use of a flux is 
necessary to prevent the formation of metallic oxid. For this 
purpose borax is usually employed. The silver, constituting, as 
it does, the greater proportion of the alloy, should be melted 
first and be covered with considerable borax. When this has 
been thoroughly fused, the other metals may be added and 
mixed by agitation or by stirring with wood. Finally, the 
solder may be cast in the usual ingot mold. 



CHAPTER XVI. 
RECOVERY OF RESIDUE. 

Gold. — The gold scrap may be recovered in two ways: 
first, by fusion with suitable flux; second, by dissolving in aqua 
regia and precipitation of the metal. In the first method it 
is necessary to remove mechanically the impurities as far as pos- 
sible, then mix the fairly clean gold waste with potassium nitrate 
and a little borax, and fuse in a clay crucible. The gold will 
separate as a button at the bottom of the thoroughly fused slag. 

In the second method the scrap gold is dissolved in aqua 
regia and the resulting solution of AuCl 3 is precipitated with 
ferrous sulphate or oxalic acid. The later precipitant, although 
working more slowly than the iron, does not precipitate platinum, 
hence in case platinum is present it is the better reagent to use. 
The precipitated gold is next filtered, thoroughly washed, and 
fused in clay crucible under borax and potassium nitrate. 

Silver. — The recovery of silver is best accomplished by 
dissolving the scrap or waste in nitric acid and precipitating as 
chlorid, then reducing the chlorid to metallic silver either by 
treatment with pure zinc or by fusion with sodium carbonate. 
If tin is present in the scrap, the nitric acid will form metastannic 
acid, a white insoluble powder rather difficult to filter. Hence, 
it is better to wash this by decantation several times with dis- 
tilled water, which will remove practically all the silver. From 
the nitric-acid solution the Ag may be precipitated by salt or 
hydrochloric acid. This precipitate must be washed till the 
wash-water is practically free from chlorin, then dried and fused 
with sodium carbonate, when a button of pure silver will be 
obtained. 

133 



134 DENTAL METALLURGY 

If preferred, the precipitated chlorid of silver may be washed 
once by decantation, then agitated with pure zinc, when the 
following reaction takes place : 

2 AgCl + Zn = ZnCl 2 + 2 Ag. 

The finely divided Ag (in the form of nearly black powder) 
must be washed free from chlorin, carefully dried and fused 
under carbonate of sodium, or, after drying, it may be weighed 
and dissolved at once if a solution is desired. If the silver residue 
contains mercury this may be driven off by heat before solution 
is attempted. 

Mercury. — Mercury which has been used in making amal- 
gams is best purified by distillation. Mercury which needs 
simply to be freed from dirt, dust, or slight traces of other 
metals may be purified as follows : If a piece of filter-paper is 
fitted closely in a glass funnel, a pin-hole made in the joint and 
the paper thoroughly wetted with water and the mercury to be 
purified placed on the paper, the heavy metal will run through 
the pin-hole, leaving practically all the dirt clinging to the wet 
filter-paper. Such mercury may also be cleansed by filtering 
through chamois-skin. 

In case the mercury contains slight amounts of other metals, 
if it is digested with a very dilute nitric acid, the acid will gen- 
erally first dissolve the impurities and afterwards a little of the 
mercury itself. Then thorough washing with water will remove 
all excess of acid and all soluble salts which may have been 
formed. Pure mercury should have no coating of any sort on 
its surface, and if a few globules are allowed to run down a 
smooth inclined plane, they should leave no "tail" behind. 

Laboratory Exercises XXX to XXXIV. 

During the study of alloys and volumetric analysis the 
student will be required to make qualitative analyses of several 
commercial alloys, dental cements, etc. He will also have to 



RECOVERY OF RESIDUE 



135 



prepare and test carefully six alloys, the formulae for which will 
be given on a mimeograph sheet similar to that represented 
below. 

The properties of the various alloys are to be carefully com- 
pared and it is often desirable for two or more students to vary 
a given formula in some one particular and note the result of 
such a variation upon the properties of the amalgam obtained. 



ALLOYS. 



Date. 



Desk No Name. 





No. 1. 


No. 2. 


No. 3. 


No. 4. 


No. 5 . 


No. 6. 


Gold 


















Silver 






18 


60 


55 








Tin 


3 


1 


65 


40 


37 








Copper 










4 




Zinc 










4 








Lead 


5 


2 














Antimony 






17 








Bismuth 


8 


4 










Cadmium 




1 

























136 DENTAL METALLURGY 

Nos. 1 and 2 contain lead and must not under any circumstances be made 
in the graphite crucible which you intend to use for silver-tin alloys. These 
are solders or fusible metals. Make 8 to 10 grams and determine melting- 
point of each. 

No. 3 is a very low grade dental alloy. Make 10 grams and test for 
expansion, discoloration, and crushing strength. 

Nos. 4 and 5 are better-grade alloys. Make 10 or 12 grams of each. 
Hand one in as sample of work; test the other, annealed and unannealed, 
as No. 3 was tested. 

No. 6, your own formula. Make 15 to 20 grams. Make complete tests 
and also return sample. Return all remaining portions of alloys with desk 
number and composition of the alloy plainly written on envelopes furnished, 
in order to obtain proper credit for the work. 



PART III. 
VOLUMETRIC ANALYSIS. 

CHAPTER XVII. 
STANDARD SOLUTIONS. 

Volumetric analysis is the determination of the quantity 
of a particular substance contained in a given sample by means 
of volumetric or standard solutions. By means of standard 
solutions, it is possible to determine easily and quickly the 
strength of a peroxid of hydrogen solution, the percentage of 
silver in an amalgam alloy, or the amount of gold in a plate 
or solder, and it is volumetric analysis thus specialized and 
adapted to dental purposes that we shall consider. 

The standard solution may be so prepared that it has an 
arbitrary or special value, such, for instance, as the silver-nitrate 
solution usually used in determining the amount of chlorin 
in urine, i c.c. of this solution being equal to 10 milligrams of 
salt (NaCl) ; or its standardization may be made with reference 
to the molecular weights of the reagents employed, so that solu- 
tions of a similar nature will be of equivalent values. That is, 
a solution containing the hydrogen equivalent of the reagent, 
weighed in grams, per liter, is known as a normal solution and 
10 c.c. of any normal acid will be of the same value in neutralizing 
an alkali as 10 c.c. of any other normal acid. On the other 
hand, 10 c.c. of a normal acid is equal to 10 c.c. of any normal 
alkali solution whatever the alkali may be. 

The normal factor is the weight of reagent contained in one 
cubic centimeter of the normal solution. 

137 



138 VOLUMETRIC ANALYSIS 

The volumetric process and the use of the normal factor 
will be most clearly understood by the explanation of a specific 
example. 

We will suppose that we have prepared a normal solution of 
NaOH and wish to ascertain the strength of a sample of dilute 
HCL The normal solution will contain the molecular weight 
in grams of NaOH per liter or 40 grams absolute NaOH. 

The molecular weight of HC1 being 36.4 (36.37), a normal 
solution of HC1 will contain 36.4 grams absolute HC1; and, if 
a liter of normal NaOH were added to a liter of normal HC1, 
exact neutralization would result: 

NaOH + HC1 = NaCl + H 2 0. 
40 36.4 58.4 18 

The 1 liter of normal alkali (containing 40 grams NaOH) 
is exactly neutralized by 36.4 grams of HC1, or 1 ex. of normal 
alkali by 0.0364 gram of HCL 0.0364 is normal factor of HC1. 

Now, if by our process of analysis we find that it takes just 
21 c.c. of the NaOH solution to exactly neutralize 10 c.c. of 
HC1 solution, 1 c.c. of NaOH being equal to 0.0364 gram HC1, 
21 c.c. of NaOH will be equal to 0.0364 X 21, or 0.7644 gram 
HC1, or 10 c.c. of the HC1 solution contains 0.7644 gram of 
absolute HC1, equivalent, approximately, to 7.64%. 

It has become apparent that in carrying out this process 
three things are absolutely necessary: 

1. Methods for the preparation of standard solutions. 

2 . Apparatus for accurate measurements of both the standard 
solution and the unknown. 

3. Means for determining just when the point of exact 
neutralization is reached. This point is known as the " end 
point" and is shown by "indicators" of various kinds. 

Preparation of Standard Solutions. — Experience has shown 
that normal solutions are in many cases less convenient to work 
with than those much more dilute, both on account of the keep- 



STANDARD SOLUTIONS 139 

ing qualities of the standard solution and the accuracy of manip- 
ulation ; and, for the purposes of dental chemistry, a decinormal or 
one- tenth normal solution represented by N/10 will generally be 
used. 

In working with an N/10 solution, the factor used in cal- 
culations of results will be one-tenth of the normal factor and 
is termed an N/10 factor. Other fractional proportions of the 
normal solution may be used as the centinormal, N/100, or 
seminormal, N/2. While the decinormal solution contains 
one-tenth of the hydrogen equivalent of reagent in grams per 
liter, and this amount is very easy to calculate, it is often very 
difficult to weigh out the exact amount required. For instance, 
we want an N/10 solution of HC1. HC1 is a gas soluble in. 
water and the strengths of the solutions vary greatly, so we can- 
not weigh out 3.637 grams of absolute HC1 to put in 1000 c.c. of 
water though we know this is just the amount necessary to 
produce our N/10 solution. Thus, one of the first practical 
difficulties in making up standard solutions is to find some 
substance which can be weighed accurately and the exact chemi- 
cal composition of which may be relied upon. 

Crystallized oxalic acid is such a compound, although care 
must be taken that the crystals are dry and yet contain all 
their water of crystallization; in other words, are actually 
represented by the formula H 2 C 2 4 , 2 H 2 0. Fused carbonate 
of sodium is another such compound. If the purest obtainable 
bicarbonate of soda is fused till no further change takes place, 
cooled, and powdered, the product is pure enough for the prep- 
aration of a standard solution for ordinary use. 

For the preparation of volumetric solutions it is necessary to 
have a balance which will weigh accurately to at least two 
decimal points. It will be much better to have a balance sen- 
sitive to one milligram. Balances of this sort inclosed in a glass 
case can be obtained at a very reasonable price. Fig. 10 on 
page 141 represents such a balance. 



140 VOLUMETRIC ANALYSIS 

It is also essential to have flasks capable of holding ioo, 250, 
500, and 1000 c.c. carefully graduated on the neck, represented 
in Fig. 11, page 141. 

Graduated cylinders (Fig. 12) are not so well suited for the 
preparation of standard solutions, as the greater breadth of the 
column of liquid makes accurate reading much more difficult. 

Small cylinders of 100 c.c. or less are useful in making up 
odd amounts of solution. 

In the process of analysis it will be necessary to have pipettes 
(Fig. 13) measuring 5 and 10 c.c, also a burette (Fig. 14), from 
which the standard solution may be used. The burettes may 
be had in a variety of styles and sizes, a very serviceable one 
being of 25 c.c. capacity and graduated in tenths of a cubic centi- 
meter. It may have a glass stop-cock or it may be furnished 
with a glass tip with rubber connector and pinch-cock. 

A set of measuring-instruments which have been carefully 
compared with one another should be kept; that is, the 1000-c.c. 
flask should be exactly filled by taking the 100-c.c. flask full to 
the mark just 10 times, thus enabling one accurately to take 
aliquot parts of any given solution. 

Indicators. 

The third requisite for carrying out a volumetric process 
is a method for determining the end point of the reaction; 
that is, we must know when there has been a sufficient quantity 
of a standard solution added to an unknown solution. Phenol- 
phthalein gives a red color with alkalis, which is discharged 
by the addition of acid till the solution becomes colorless as 
it becomes neutral or acid. Litmus gives a blue color with 
alkalis and a red with acids; Methyl orange can be used with 
carbonates and mineral acids; it does not work so well with 
organic acids. The color is pink in acid and yellow in alka- 
line solution. Lacmoid is useful in cases where the acid proper- 
ties of such salts as alum or zinc chlorid might interfere with 



STANDARD SOLUTIONS 



141 




Fig. 10. 



Fig. 11. 




t 




Fig. 12. 



Fig. 13. 



Fig. 14. 



142 VOLUMETRIC ANALYSIS 

the use of litmus or phenolphthalein. The different indicators 
do not all change color at exactly the same point in the process 
of neutralization, and it is possible for a solution to be alka- 
line to litmus and acid to phenolphthalein at the same time. 
Hence uniformity in the use of indicators is desirable. In 
physiological chemistry, Congo red, tropaeolin oo, and dimethyl- 
aminoazobenzol are also used. 

The end point may be indicated by excess of a standard 
solution if it happens to be highly colored, as potassium per- 
manganate. Thin starch paste is used as an indicator in oper- 
ations involving the use or liberation of free iodin. Other indi- 
cators will be considered as we have occasion to use them in the 
various analytical processes. 

The process of volumetric analysis may be divided into 
three classes: First, acidimetry and alkalimetry. Second, oxi- 
dation and reduction. Third, precipitation. 

Acidimetry and Alkalimetry. 

Acidimetry and alkalimetry includes all standardized solu- 
tions, either acid or alkaline, which may be used in neutralizing 
solutions of unknown strength of an opposite character. For 
instance, the strength of vinegar is determined by neutralizing 
a known volume with standard alkali. 

For present purposes two standard acids and one standard 
alkaline solution will be sufficient. The first of these may be 
decinormal oxalic solution prepared from recently recrystallized 
and carefully dried acid. The composition of these crystals 
should be H 2 C 2 4 2 H 2 0, having molecular weight of 126. This 
being a dibasic acid it will be necessary to divide the molec- 
ular weight by 2 for a decinormal solution and then again by 
10 to obtain the number of grams which must be dissolved in 
1 liter of water. For class use, each student may prepare 500 c.c. 
of this solution by dissolving 3.15 grams of pure crystallized 
oxalic acid in water and dilute to a half-liter. The graduated 



STANDARD SOLUTIONS 143 

flasks are usually constructed to be used at a temperature of 
6o° F. or 1 5 C. and for accurate work solutions must be brought 
to this temperature. After the oxalic acid solution has been 
prepared the decinormal alkali may be made as follows: 

Weigh out carefully 2 J grams of caustic soda or 3 grams 
of caustic potash and dissolve in less than 500 c.c. of dis- 
tilled water. After the solution has thoroughly cooled, fill a 
burette with it. Place 10 c.c. of standard acid previously 
prepared in a white porcelain dish of about 250 c.c. capacity, 
add 50 c.c. distilled water and 2 or 3 drops of phenolphthalein 
(2% phenolphthalein in alcohol and water, equal parts); then 
carefully run in from the burette, with constant stirring, the 
alkali solution until a permanent pink tint is produced. 

The work will be more satisfactory if the titration is made 
for the appearance of color rather than the disappearance of 
color, as would have been the case had the standard acid run 
into the measured alkali solution. This process is known as 
"titration," and will hereafter be so designated. 

The Calculation. — Supposing it has taken 8.2 c.c. of the alkali 
to exactly neutralize the 10 c.c. of N/10 acid, it follows that 
in the 8.2 c.c there is sufficient alkali to equal or to make 10 c.c. 
of an N/10 alkali solution; hence we may add 1.8 c.c. of dis- 
tilled water to every 8.2 c.c. of alkali solution, thereby reducing 
it to decinormal strength. Practically we should take 410 c.c. 
of alkali solution and in a graduated flask make it up to 500 c.c. 
with distilled water. It will be necessary to make several 
titrations and average the results before making the calculation. 

From the standard alkali N/10 solutions of HC1 or H 2 S0 4 
may be prepared in a similar manner, it being impossible to 
accurately weigh either of these two acids. In titrating a car- 
bonate, if an indicator, such as phenolphthalein, which is sensi- 
tive to carbonic acid, is used, it is necessary to keep the solution 
at a boiling temperature or at least bring it to a boil after every 
addition from the burette. 



144 VOLUMETRIC ANALYSIS 



EXAMPLE OF ACIDIMETRY AND ALKALIMETRY. 

Determine the strength of a sample of vinegar as follows: 
Measure accurately into a white porcelain dish of 150-250 
c.c. capacity 1 c.c. of the sample. This may be measured either 
with a carefully graduated i-c.c. pipette or more accurately 
by diluting 10 c.c. of the sample to 100 c.c. in a graduated flask, 
then using 10 c.c. of the dilution for the titration, the titration 
to be performed with N/10 NaOH, using phenolphthalein as an 
indicator. 

The molecular weight of acetic acid is, in round numbers, 
60; hence the N/10 factor of acetic acid will be 0.006 (acetic 
acid being monobasic, HC 2 H 3 2 ). To ascertain the strength 
of the sample of vinegar it is necessary to multiply the number 
of cubic centimeters used by this factor, 0.006, which will give 
the amount of absolute acid calculated as acetic in 1 c.c. (prac- 
tically 1 gram) of the sample. Thus, if 8 c.c. of N/10 alkali 
were required to neutralize 1 c.c of vinegar, multiplying the 
factor 0.006 by 8 would give 0.048 gram of absolute acetic acid 
in 1 c.c. of vinegar, which is equivalent to 4.8%. 

Carbonate Titration. 

While perhaps phenolphthalein is the most serviceable of all 
indicators in common use, it is so sensitive to carbon dioxid that 
any titration which results in the liberation of C0 2 must be 
modified by boiling the solution thoroughly after each addition 
of acid. This makes the operation somewhat tedious, but it is 
to be preferred to the use of other and less sensitive indicators 
which may not be affected by the carbon dioxid. 

Analysis by Oxidation and Reduction. 

If to a hot solution of oxalic acid containing sulphuric acid, 
permanganate of potash be added, the following reaction takes 
place: 



STANDARD SOLUTIONS 145 

2 KMn0 4 + 5 H 2 C 2 4 + 3 H 2 S0 4 = K 2 S0 4 + 2 MnS0 4 
+ 10 C0 2 + 8 H 2 0. 

This reaction represents a very valuable method of volumetric 
analysis; but, inasmuch as it is not a process of neutralization, 
it cannot properly come under the head of acidimetry and alka- 
limetry, but rather under a distinct classification, the determina- 
tion involving oxidation and reduction. 

Standard Permanganate Solution. — In the reaction given 
above we may consider that, as the molecule of K 2 Mn 2 8 breaks 
up, three of the eight atoms of oxygen are required to form the 
basic oxids K 2 and 2 MnO (soluble in the acid as K 2 S0 4 and 
2 MnS0 4 ), while the remaining five atoms are liberated and 
constitute the active chemical agent whereby the oxalic acid is 
oxidized to C0 2 and H 2 0. Hence, to reduce this double molec- 
ular weight (316) to the hydrogen equivalent necessary for a 
normal solution, it is divided by 10 (five atoms of oxygen having 
a valence of 10). 

The Decinormal Solution may be made by dissolving 3.16 
grams of pure recrystallized and thoroughly dried crystals, if 
they can be obtained, in distilled water, and making the solu- 
tion up to 1000 c.c, or it may be standardized by titration with 
the N/10 oxalic acid previously prepared; in this case one would 
proceed as follows: 

Make a solution slightly stronger than the standard required, 
say about 3.5 grams of the ordinary pure crystals in a liter of 
water; with this fill a burette, place 10 c.c. of N/10 oxalic acid 
measured from a pipette in an evaporating-dish or casserole, 
dilute with about 50 c.c. of water, add about 10 c.c. of dilute 
sulphuric acid, and heat the mixture nearly to the boiling-point. 
Then titrate with the permanganate from the burette. The 
permanganate will at first be rapidly decolorized, but as the 
operation progresses the color fades more slowly till at last a 
faint permanent pink color indicates that the "end point" has 
been reached. 



146 VOLUMETRIC ANALYSIS 

The temperature must be kept above 6o° C. throughout the 
titration or the oxidation will take place too slowly and an 
apparent end point will be obtained before the reaction is com- 
pleted. 

If the solution turns muddy during the operation, it is due 
to an insufficient amount of sulphuric acid and more should 
be added. The calculation is made as in the case of the N/10 
NaOH described on page 143. The standard permanganate 
should be preserved in full, well-stoppered bottles and kept 
in a dark place. 

It is better to have the KMn0 4 solution made up a day or 
two before it is standardized, thereby oxidizing traces of am- 
monia, etc., which the water may contain. 

DETERMINATION OF PEROXID OE HYDROGEN. 

In determining the strength of peroxid use 1 c.c. of the 
sample measured as in the case of vinegar (which see), dilute 
with 50 c.c. of distilled water, add 10 c.c. of dilute sulphuric 
acid, and titrate with the permanganate in exactly the same 
manner as detailed in the preceding paragraph, the reaction in 
this case being as follows: 

2 KMn0 4 + 5 H 2 2 +3 H 2 S0 4 = K 2 S0 4 + 2 MnS0 4 +5 2 +8 H 2 0. 

The aqueous solutions of peroxid on the market used as 
antiseptics contain about 3% absolute H 2 2 and yield approxi- 
mately ten volumes of available oxygen; that is, 10 c.c. of solu- 
tion will yield 100 c.c. of oxygen. The calculation may be 
made to express strength of the peroxid in terms of percentage 
of absolute H 2 2 by multiplying the number of cubic centimeters 
of N/10 KMn0 4 decolorized by 1 c.c. of solution by 0.17, or to 
express the strength in volumes of available oxygen by multiply- 
ing the number of cubic centimeters of solution by 0.56 (more 
accurately 0.5594). 






STANDARD SOLUTIONS 1 47 

DECINORMAL IODIN. 

A decinormal solution of iodin may be prepared by dis- 
solving 12.68 grams of pure iodin crystals in one liter of water 
by the aid of about 18 grams of pure potassium iodid. 

Iodin of sufficient purity may be obtained by carefully re- 
subliming selected and carefully dried crystals of so-called 
" chemically-pure " iodin. 

DECINORMAL SODIUM THIOSULPHATE. 

Na 2 S 2 3 .5 H 2 = molecular weight, 248.24. This solution 
may be made by weighing directly 24.824 grams of the pure 
crystallized salt, dissolving in water and diluting to 1000 c.c, or 
it may be standardized by titration with a decinormal iodin 
solution, the reaction being as follows : 

2 Na 2 S 2 3 + 2 I = 2 Nal + Na 2 S 4 6 . 

The indicator used is a very dilute starch paste, which gives 
the characteristic blue color as soon as free iodin is in excess. 

By means of these two standard solutions (iodin and sodium 
thiosulphate) a variety of determinations may be made with 
great accuracy. Any substance which will liberate iodin from 
potassium iodid may be quantitated by adding an excess of 
the potassium salt and titrating the free iodin with thiosulphate 
solution, using starch paste as usual for an indicator. 

Peroxid of hydrogen may be thus determined as easily as 
by the permanganate method previously given. The process, 
being that of Kingzett, is given as follows by Sutton: 

Mix 10 c.c. of peroxid solution to be examined with about 
31 c.c. of dilute sulphuric acid (1-2) in a beaker, adding crystals 
of potassium iodid in sufficient quantity, and after standing 
rive minutes titrating the liberated iodin with N/10 thiosul- 
phate and starch. The peroxid solution should not exceed the 
strength of two volumes; if stronger, it must be diluted pro- 
portionately before the analysis. 



148 VOLUMETRIC ANALYSIS 

In the case of a very weak solution it will be advisable to 
titrate with N/100 thiosulphate. 

1 c.c. N/10 thiosulphate = 0.0017 gram H 2 2 or 0.0016 
gram. 

VOLUMETRIC DETERMINATION OF ARSENIC. 

Mohr's method of oxidation with iodin is a practical one. 
The titration is made with N/10 iodin and starch as usual, 
except that the solution should be at first neutral and then 
about 20 c.c. of saturated solution of sodium bicarbonate should 
be added to every 0.1 gram of As 2 3 supposed to be in the un- 
known, thus giving a certain definite alkalinity. If the solution 
is acid, neutralize with sodium bicarbonate, then make alkaline 
with more bicarbonate as above. 

VOLUMETRIC DETERMINATION OF GOLD. 

(See also p. 154.) 

While gold is usually determined quantitatively by assay 
in a dry way (page 157) it may be determined very accurately 
by titration with thiosulphate solution. Fatka (Chem. Zeit.) 
recommends the following process based upon the facts that 
a neutral solution of gold salt with potassium iodid will give 
a greenish precipitate. When an excess of potassium iodid 
is used no precipitate is formed, but a solution of Aul 3 as AuKI 4 
results. This is of a brown color and may be titrated with 
N/10 thiosulphate solution, when the following reaction takes 
place : 

AuKI 4 + 2 Na 2 S 2 3 = AuKI 2 + 2 Nal + Na 2 S 4 6 . 

Process: 10 c.c. of gold solution containing approximately 
2% of gold is treated with 4 grams of potassium iodid diluted 
to 100 c.c. with water and titrated with N/10 Na 2 S 2 3 solu- 
tion, using starch as an indicator. 

Analysis by Precipitation. 
Because certain elements possess a selective affinity for 
other elements it is possible to determine many substances 



STANDARD SOLUTIONS 149 

quantitatively by precipitation. That is, if silver nitrate is 
added to a mixture of a soluble chlorid and a chromate, the 
chlorin will combine first with the silver, forming AgCl, to the 
exclusion of the chromate. After the last trace of chlorin has 
been so combined, then the silver chromate will be formed, 
which is a salt with an intense red color; hence it is possible to 
determine the strength of solutions of soluble chlorids by titra- 
tion with standard AgN0 3 , using potassium chromate as an in- 
dicator. This process is used in analysis of drinking-water, of 
saliva, and of urine, but for each of these it is desirable to have 
solutions of special strength. 

A DECINORMAL SILVER SOLUTION 

may be made by dissolving 17 grams of pure crystallized 
AgN0 3 in a liter of distilled water, and with this a 

DECINORMAL SODIUM CHLORID SOLUTION 

may be prepared as follows : 

Weigh out 6 grams of the purest salt obtainable and dis- 
solve in approximately 1 liter of distilled water. With a pipette 
measure 10 c.c. of this solution into a white porcelain dish, dilute 
to about 20 c.c. with H 2 0, add two to five drops of neutral 
potassium chromate (K 2 Cr0 4 ) and add AgN03 from a burette 
till a faint pink color persists. 

The calculation and dilution is made exactly as described 
on page 143 in the preparation of a standard NaOH so]ution. 
The silver nitrate solution used to determine chlorin in urine 
is usually prepared of such a strength that 1 c.c. precipitates 
just 10 milligrams of sodium chlorid. This is equivalent to 
0.006065 gram of chlorin. A solution of this strength is pro- 
duced when 29.075 grams of pure, fused silver nitrate are 
dissolved in sufficient distilled water to measure 1 liter of solu- 
tion. If chlorin is to be determined in drinking-water, it is 
usually necessary to concentrate the water at least 1/5 its bulk 



150 VOLUMETRIC ANALYSIS 

and then use not more than one or two drops of neutral chro- 
mate as indicator. The standard silver nitrate for this titra- 
tion should be very dilute. A convenient solution may be 
prepared by diluting the standard AgN0 3 for urine i to 10. 
In saliva the sample may be diluted with an equal volume of 
water and titrated the same as in the case of drinking-water. 
In all quantitative processes where silver chromate is used to 
determine the end point the solution must be practically neutral, 
as the formation of this salt is prevented by either acids or alkalis. 

Volumetric Determination of Silver by Standard 
Potassium Sulphocyanate Solution. 

Silver may be determined volumetrically in nitric acid 
solution by titration with standard KCyS solution, using ferric 
alum as an indicator. The sulphocyanate solution must be 
standardized against decinormal AgN0 3 as follows: Prepare a 
solution containing not less than 10 grams of chemically pure 
KCyS per liter. Place this solution in the burette and put in 
the porcelain dish 10 c.c. of decinormal AgN0 3 which has been 
strongly acidified with nitric acid and 15 or 20 drops of a solu- 
tion of ferric alum, added as an indicator. The end point is 
indicated by the faint red color of ferric sulphocyanate, pro- 
duced by the first excess of KCyS. The calculation will be the 
same as previously described in the preparation of N/10 NaOH 
(page 143). 

Now, to determine the silver in solution of an alloy, take a 
measured volume of the filtrate, about 30 c.c, and put in a 
porcelain dish and add the indicator as above. 

Then place the standard KCyS in the burette and titrate 
till the faint red color is produced. 

Suppose 8 c.c of KCyS is used. The weight of silver in 1 c.c. 
of a decinormal solution is 0.0108 gram. Multiplying 8 by 
0.0108 = 0.0864. Divide by number of c.c. of solution taken, 
0.0864 -r- 30 = 0.00288 gram Ag in 1 c.c. of solution. 



STANDARD SOLUTIONS 15 1 

Multiply by whole number of cubic centimeters and divide 
by weight of alloy taken and result will be percentage of silver. 

VOLUMETRIC DETERMINATION OF COPPER. 

Into a solution of copper, free from other metals of Group I 
or II, pass H 2 S gas. Wash the resulting copper sulphid thor- 
oughly with H 2 S water, and dissolve in dilute nitric acid; then 
wash the paper in warm water, add to the filtrate (wash water) 
sodium carbonate until precipitate formed is nearly dissolved; 
then add 1 c.c. of dilute NH 4 OH. Titrate, to complete dis- 
appearance of blue color, with KCN solution previously stand- 
ardized after this same method against pure copper wire. A 
little practice is required in determining the end point to give 
the process any degree of accuracy. An excess of ammonia should 
be avoided, as it interferes with the accuracy of the end point. 

VOLUMETRIC DETERMINATION OF ZINC. 

The solution from which silver and copper have been re- 
moved, together with all wash- water, may be concentrated; 
if acid in reaction it should be evaporated to dryness, and the 
residue dissolved in water; then add a fairly strong solution 
of oxalic acid and an equal volume of strong alcohol. Allow 
to stand 15 to 30 minutes, filter, and wash with 70% alcohol till 
oxalic acid is removed, dry until the alcohol has disappeared, 
dissolve in dilute sulphuric acid, and titrate the solution with 
N/10 permanganate and calculate the zinc from the amount 
of oxalic acid found. 

This method is usually fully as satisfactory as the gravi- 
metric determination given on page 156. 

Volumetric Methods Applicable to Analyses of Saliva or 

Urine. 

DETERMINATION OF CHLORIN. 

Chlorids may be determined, without separating other con- 
stituents, by titration with silver nitrate, using neutral potassium 



152 VOLUMETRIC ANALYSIS 

chromate as an indicator, according to the method indicated 
on page 149, or a more accurate determination may be made 
by a double titration as follows: To 5 or 10 ex. of solution 
add an excess (10 or 15 c.c.) of standardized silver nitrate; 
then adding a little nitric acid to prevent precipitation of the 
phosphates, etc., and a solution of ferric alum as an indicator, 
titrate the mixture with a solution of potassium sulphocyanate 
KCyS. 

If the sulphocyanate solution has been standardized, so 
that it is the same relative strength as the silver nitrate used, 
the number of cubic centimeters of the KCyS required may be 
subtracted directly from the number of cubic centimeters of 
AgN0 3 added, and the difference will represent the amount 
of silver nitrate required to precipitate chlorin in the quantity of 
fluid taken. 



VOLUMETRIC DETERMINATION OF CALCIUM. 

This method is based upon that recommended by Dr. Percy 
R. Howe, Dental Cosmos, April, 191 2. To 5 c.c. of saliva, add as 
much more distilled water and a slight excess of oxalic acid 
or ammonium oxalate (5 c.c. of normal solution will be sufficient). 
Add ammonium water to alkaline reaction, heat nearly to the 
boiling point, and allow to stand for 20 to 30 minutes. Filter 
through a hardened filter paper into a small beaker which is 
allowed to stand on a piece of black glazed paper. Under these 
circumstances, a slight rotary motion of the beaker will show 
if any of the white precipitate of calcium oxalate is passing 
through the paper. 

After filtration is complete, wash five times in hot distilled 
water; then place the precipitate, together with the paper, into 
a small beaker, add about 30 c.c. of dilute sulphuric acid, and 
heat nearly to the boiling point; then titrate with N/20 perman- 
ganate solution. 



STANDARD SOLUTIONS 153 

VOLUMETRIC DETERMINATION OF PHOSPHORIC ACID. 

The determination of total phosphoric acid, calculated as 
P 2 5 , requires the following solutions: 

A standard uranium solution, containing 35.5 grams of pure 
uranium nitrate or acetate in distilled water sufficient to make 
1000 c.c; next an acid solution of sodium acetate, containing 
10% of sodium acetate and 3% of acetic acid, and lastly a 
saturated solution of potassium ferrocyanide, to be used as an 
indicator. 

Process (as given by Ogden's Clinical Examination of 
Urine) : Take 30 c.c. of the urine in a porcelain evaporator, 
add 5 c.c. of the sodium acetate solution, and heat the mixture 
to 8o° C. over a water-bath. Titrate the hot mixture slowly 
with standard uranium solution until a drop from the evapora- 
ting dish placed on a porcelain tile with a drop of the potassium 
ferrocyanide gives a distinct brown color. When this point is 
reached the number of cubic centimeters of uranium solution 
used is noted and multiplied by 0.005 which will give the quan- 
tity of phosphoric acid in 30 c.c. of urine, and from this one can 
calculate the percentage of total phosphoric acid. 

This same process may be used for saliva by diluting the 
reagent 1 part to 5, and preparing the sample for titration as 
follows: Take from 2 to 5 c.c. saliva, add sufficient alcohol to 
make 10 c.c of mixture, warm and filter. This serves to separate 
the protein substance. Take 5 c.c. of the filtered solution and 
titrate with the diluted uranium solution as by the process given 
above for urine. In this case, of course, 1 c.c. of the standard 
uranium will represent 1 milligram of P 2 5 rather than 5. 

GRAVIMETRIC DETERMINATIONS. 

Gravimetric determinations are, as a rule, more accurate 
than volumetric; but they require greater care and attention 
to details, making them less satisfactory in the hands of the 



154 VOLUMETRIC ANALYSIS 

beginner. Some determinations, however, on account of diffi- 
culties in obtaining accurate end points and absolute separations, 
are really easier when made by gravimetric processes. A few 
of these will be given. 

GRAVIMETRIC DETERMINATION OF TIN AS Sn0 2 . 

Tin may be separated from dental alloys in the absence of 
gold or platinum by simply dissolving the alloy in nitric acid. 
Tin will remain as a white insoluble metastannic acid. As stated 
on page 33 metastannic acid, upon long standing, will change to 
somewhat soluble compounds, hence this operation should be 
completed with reasonable rapidity. After complete disintegra- 
tion of the alloy, the insoluble tin compound may be separated 
by nitration through asbestos fiber, contained in a Gooch cruci- 
ble. The method of procedure is as follows: 

A little fine asbestos fiber, washed in acid and held in sus- 
pension in water, is placed on the bottom of the crucible. The 
crucible is then placed in the top of a filtering flask from which 
the air is exhausted by the suction pump. This packs the 
asbestos down firmly on the bottom of the crucible in a thin 
layer, and care should be taken that the quantity of asbestos 
used is such that water will pass through it easily. The cruci- 
ble with asbestos is next dried, ignited, and weighed. Now 
transfer the precipitate of tin oxid (metastannic acid) to the 
crucible, taking care that none is lost, and wash thoroughly six 
or eight times, then dry, ignite strongly, and weigh again. 

If the ignited residue, weighed as tin oxid, does not contain 
gold or platinum, the weight of tin may be obtained by multi- 
plying the weight of the ash by 0.788. 

VOLUMETRIC DETERMINATION OP GOLD. 

If the residue of tin oxid does contain gold, it should be 
separated and its weight deducted before the calculation for 
Sn is made as above. This separation may be made by the 



STANDARD SOLUTIONS 155 

fire assay as given on page 157, or by solution in aqua regia 
and subsequent precipitation with oxalic acid, according to the 
following method as given by Schimpf in his Manual of Volu- 
metric Analysis. 

The gold must be in the form of chlorid (AuCl 3 ). 

To the solution of gold chlorid a measured excess of N/i oxalic 
acid solution is added and the mixture set aside for twenty-four 
hours. 

The solution is then made up to a definite volume (say 300 
c.c). Then, by means of a pipette, 100 c.c. are removed, and 
the excess of oxalic found by titrating with N/10 permanganate 
in the presence of sulphuric acid. The reaction is 

2 AuCl 3 + 3 H 2 C 2 4 = 2 Au + 6 HC1 + 6 C0 2 . 

Each cubic centimeter of N/i oxalic acid solution = 0.06523 
gram of Au, or 0.1004 gram of AuCl 3 . 

GRAVIMETRIC DETERMINATION OF SILVER. 

The gravimetric determination of silver is not difficult, and 
is rather more accurate than the volumetric method. The silver 
is obtained in the form of AgCl. This is separated by filtration 
through an ashless paper, and dried. Then the dried precipitate 
is removed as completely as possible onto a square of black 
glazed paper and preserved under a funnel or bell glass. The 
filter paper, containing traces of AgCl which could not be re- 
moved, is next incinerated in a previously weighed porcelain 
crucible. 

As slight reduction of AgCl to Ag may take place during 
the ignition of the paper, it is necessary to add, after the paper 
is completely burned, a drop or two of nitric acid, and after the 
excess has been driven off by gentle heat, a drop or two of HC1. 
This treatment dissolves any reduced silver and reprecipitates 
AgCl. After carefully heating to dry the precipitate in the 
crucible, the reserved portion of silver chlorid is carefully brushed 



156 VOLUMETRIC ANALYSIS 

into the crucible and the whole ignited until the silver chlorid 
begins to fuse. It is then cooled and weighed as AgCl. 

GRAVIMETRIC DETERMINATION OF COPPER. 

Copper may be determined quite easily by electrolysis of 
the faintly acid (H 2 S0 4 ) solution. The copper solution must be 
freed from other metals and preferably be obtained as a solu- 
tion of copper sulphate of approximately 0.1 of 1% of copper. 
50 c.c. of such a solution are put into a platinum dish which 
is placed upon a copper plate connected with the negative pole 
of a battery. A strip of platinum suspended from the positive 
pole is immersed in the solution and the current allowed to pass 
for from three to twelve hours, according to the strength of the 
copper solution. The ordinary no- volt (direct) current em- 
ployed for electric lighting may be used by introducing a re- 
sistance of from three to six 16-c.p. lamps. After the copper has 
been entirely deposited the residual solution is drained out of the 
platinum dish, a little alcohol added, which is also drained out, 
and by setting fire to the last traces of alcohol the precipitated 
copper is dried and in condition to weigh. Care must be taken 
to avoid oxidation of the finely divided Cu ; if it turns black too 
much heat has been used and partial oxidation has taken place, 
which has of course resulted in an increase of weight. 

GRAVIMETRIC DETERMINATION OF ZINC. 

Zinc may be determined gravimetrically by precipitation as 
zinc sulphide as follows: To a measured portion of the solution, 
free from all metals (except zinc) of Groups I, II, III, and IV, 
add ammonium chlorid, ammonium hydroxid, and ammonium 
sulphid, as in qualitative analysis. Filter the precipitated ZnS 
on to counterpoised filters, wash thoroughly with water con- 
taining a little ammonium sulphid, dry in an atmosphere free 
from oxygen, (hydrogen or hydrogen sulphid), and weigh as 
ZnS. 



ANALYSIS OF ALLOYS 1 57 

Gravimetric Assay of Gold and Silver in the Dry Way. 

It is often more convenient to determine gold and silver by 
the fire assay than by the volumetric methods previously given. 
This is accomplished usually by fusion with an excess of lead 
and a borax flux. The mixture is kept at a high heat for up- 
wards of thirty minutes, with a current of air passing over the 
surface of the molten metals. This serves to oxidize and carry 
away the baser metals, leaving the gold and silver with but a 
slight amount of lead, possibly a trace of copper and tin. The 
purification is completed by cupellation. When the traces of 
lead and other metals are absorbed by the cupel or are driven 
off as volatile oxids, the button of gold and silver is next cooled 
very slowly and carefully weighed. From this the silver may be 
dissolved by nitric acid unless the gold is in considerable excess, 
which would rarely be the case. If it happens that the gold 
is present in sufficient quantity to prevent the solution of the 
silver in nitric acid a known weight of pure silver may be added 
in amount sufficient to, increase the percentage of silver to 75 
or over, fused, and then all the silver dissolved out with HNO3, 
leaving the gold. 

The gold which has resisted solution may be found as small 
black particles or grains in the bottom of the crucible. This 
should be carefully washed with distilled water by decantation, 
very carefully dried and brought to a red heat, which will give 
a button of pure gold. This may be weighed and the weight 
subtracted from the weight of gold and silver button previously 
obtained. 

QUANTITATIVE ANALYSIS OF DENTAL ALLOYS CON- 
TAINING Au, Sn, Ag, Cu, Zn. 

Weigh accurately 0.5 of a gram of alloy which has been re- 
duced to fine filings and from which all particles of iron have 
been carefully removed by a magnet, transfer to a beaker and 



158 VOLUMETRIC ANALYSIS 

dissolve in 15 c.c. of strong HN0 3 and 10 c.c. of H 2 by aid of 
gentle heat. If the sample contains tin or gold, complete solu- 
tion will not be effected, but, by watching the character of the 
sediment through the bottom of the beaker, it is possible easily 
to determine when the alloy has been completely disintegrated. 

If silver is to be determined by titration with NaCl and 
KoCr0 4 , evaporate on a water-bath till all nitric acid has been 
expelled. 

If silver is to be determined by the sulphocyanid solution, 
evaporation at this point is not necessary. In either case, make 
the whole solution up to 250 c.c. with distilled water; then filter 
out tin and gold, following the method given under gravimetric 
determination of tin (page 154), reserving the filtrate before any 
wash-water has been added. For convenience this filtrate may 
be marked "A". Titrate 25 or 50 c.c. of this filtrate ("A") 
for silver (page 150.) 

Take 100 c.c. of filtrate " A" and precipitate silver by slight 
excess of HC1. Filter and wash precipitate thoroughly with 
warm water. Concentrate filtrate and wash-water, which may 
be designated as filtrate "B." Pass H 2 S gas into "B" till 
copper is entirely separated as CuS. Filter and wash CuS 
seven or eight times with dilute H 2 S water. Reserve filtrate 
and wash- water as filtrate " C". Dissolve CuS in dilute HNO3, 
wash paper carefully, concentrate and determine amount of 
copper by deposition upon platinum (page 156). Concentrate 
filtrate "C" and determine Zn by volumetric method given on 
page 151. 

During the study of volumetric analysis, taking probably 
about two weeks' time, consequently covering twelve Labor- 
atory exercises (Nos. 35 to 46 inclusive), the student will be re- 
quired to make the various standard solutions, to use them more 
or less on solutions of unknown strength, and to make a complete 
quantitative analysis of at least one dental alloy. 



PART IV. 
MICROCHEMICAL ANALYSIS. 

CHAPTER XVIII. 
METHODS. 

The advantages of microchemistry are many, as claimed by 
its enthusiastic advocates, and there are two particulars in which 
these methods strongly recommend themselves to the dental 
practitioner: (i) Microchemical analysis deals with exceedingly 
minute portions of matter, making the examination of very 
small particles of substance easily possible. (2) Three or four 
one-ounce "drop-bottles" and a few two-drachm vials will 
contain all necessary reagents, and in consequence three feet 
of bench-room will furnish ample laboratory space. 

The principles of microchemical analysis are, of course, the 
same as for any analysis, but the processes employed are quite 
different and need some explanation. In microchemical analysis 
the production of crystals of characteristic form furnishes per- 
haps the most rapid method of detection of an unknown sub- 
stance, and in this we are greatly aided by the use of polarized 
light, which not only helps in the differentiation of crystals but 
often makes it possible to see and distinguish small or trans- 
parent crystals which might otherwise escape notice altogether. 

Use of Microscope. — For the examination of the crystals 
mentioned in this chapter, also for the work required on saliva 
or urine, lenses of comparatively low power are sufficient. For 
most of the microchemical tests, a No. 3 Leitz or a 16 mm. Bausch 
& Lomb objective will be found satisfactory. For a few micro- 

159 



160 MICROCHEMICAL ANALYSIS 

chemical tests and for urine, a M-inch Bausch & Lomb or a 
No. 5 Leitz objective will give better results in the hands of a 
beginner than one of higher power. 

In using the microscope for microchemistry, the preparation 
should always be covered with a cover glass and the examination 
be made with the low-power lens if possible. The object in 
covering is to prevent any action by reagent upon the objective. 
As a further precaution, it is well to form the habit of first 
lowering the objective and then focusing by upward movement 
of the draw- tube. 

Formation of crystals may be brought about in two ways: 
first, by precipitating insoluble crystalline salts by use of re- 
agents, as in ordinary qualitative analysis; second, by allowing 
salts to crystallize by spontaneous evaporation of the solvent. 

If the first method is to be employed it is essential to have 
the dilution fairly constant in order to obtain crystals which shall 
be comparable with those obtained at other times or by other 
individuals. The tendency of strong solution is to give amor- 
phous precipitates. Sometimes the precipitate will be amor- 
phous when first thrown down, but upon standing will assume 
crystalline form. To secure the uniformity of results necessary 
to correct deductions, the following method of procedure should 
be exactly followed every time. 

The reagent should be of uniform strength, usually i or 2 per 
cent. Place on a clean microscope-slide a small drop of the solu- 
tion to be tested, and as close as possible without touching it, one 
of about equal size of the reagent to be used. Now bring the 
drops together by tapping the slide or with a small glass rod. . If 
a precipitate forms immediately, cover with a cover-glass (this 
must always be done) and examine with the microscope. If the 
precipitate is crystalline, note the form, and in any case, whether 
crystalline or not, repeat the test after diluting the unknown 
solution one-half. If the second test gives an amorphous pre- 
cipitate, or crystals of different shape from the first, continue 



METHODS 161 

the dilution of the unknown till a point is reached when admixture 
with the drop of reagent gives no immediate precipitate, but one 
appearing in a few seconds' time (five to thirty). In this way 
we have produced the precipitate under standard conditions or 
as nearly such as is possible with unknown solutions. 

Until thoroughly familiar with the forms obtained by drying 
the various reagents, it is well to evaporate a small drop of the 
reagent alone, on the same slide on which a test is made, for the 
sake of subsequent comparisons. 

Filtration in microchemical examinations, when perhaps only 
a few drops of solution are to be had, may be effected in a very 
satisfactory manner and without appreciable loss by absorption 
as follows: 

Cut a filter-paper about i cm. wide and 6 cm. long, double 
it and crease the middle so that it assumes the shape of an in- 
verted V. Put the solution to be filtered in a small watch- 
glass placed at a slight elevation above a microscope slide; 
now place one "leg" of the strip of filter-paper in the watch- 
glass, allowing the end of the other to touch the slide. By 
capillary attraction the clear solution will follow over the bend 
in the strip of paper and a drop or two of perfectly clear filtrate 
suitable for the test will be found upon the slide. 

Evaporation of a solution is best effected on a small watch- 
glass held in the fingers and moved back and forth over a low 
Bunsen flame, or else placed over a water-bath. 

The purpose of the microchemical tests here outlined is not 
so much a method of general qualitative analysis, to which they 
are not suited, as it is a specific application of well-known reac- 
tions to concrete examination of substances, the uses and prob- 
able composition of which are known. The details of the various 
tests will be given under classification furnished by the sub- 
stances investigated. 

Our study may include alloys and amalgams, teeth, tartar, 
dental anaesthetics, cement, mouth-washes, antiseptics, disin- 



162 MICROCHEMICAL ANALYSIS 

fectants, and sediments obtained from the saliva and from the 
urine. 

The following crystals are selected as among those most 
frequently met with in the analysis of the above substances or 
best suited for the study of microchemical processes, and the 
student should make each test here indicated and carefully 
draw the crystals produced: 

i. Calcium oxalate from 2% H2C2O4 and CaCl 2 solutions 
(Plate II, Fig. 1). 

2. Cadmium oxalate from 2% H2C2O4 and CdSC>4 solutions 
(Plate II, Fig. 2). 

3. Strontium oxalate from 2% H 2 C 2 4 and Sr(NOs) 2 solu- 
tions (Plate II, Fig. 3). 

4. Sodium oxalate by evaporation of aqueous solution, also 
by evaporation of urine containing Na 2 C 2 4 (polarized light) 
(Plate II, Fig. 4). 

5. Urea oxalate from 2% H 2 C 2 4 and urea solution (Plate 
II, Fig. 5). 

6. Ammonium-magnesium-phosphate from magnesium mix- 
ture * and sodium phosphate (Plate IV, Fig. 2). 

7. Ammonium platinic chlorid (Plate III, Fig. 1). 

8. Ammonium phosphomolybdate from ammonium molyb- 
date and phosphate of sodium (Plate III, Fig. 2). 

9. Sodium urate by evaporation (polarized light) (Plate X, 
Fig. 3, opp. page 368.) 

10. Crystals formed from cocain and potassium perman- 
ganate (Plate III, Fig. 4). 

n. Crystals formed from carbolic acid and dilute bromin 
water (tribromphenol) (Plate III, Fig. 5). 

12. Crystals formed from morphin solutions and ammo- 
nia (morphia) (Plate III, Fig. 6). 

* Magnesium mixture as used in urine analysis to precipitate phosphates 
contains MgCl 2 (or MgS0 4 ), NH 4 C1 and NH 4 OH. 



PLATE II. — MICROCHEMICAL ANALYSIS. 




Fig. i. 

Calcium Oxalate. 




Fig. 3. 
Strontium Oxalate. 





Fig. 2. 

Cadmium Oxalate. 




Fig. 4. 
Sodium Oxalate (P.L.). 




Fig. 5. 
Oxalate of Urea. 



Fig. 6. 
Zinc Oxalate. 



PLATE III. — MICROCHEMICAL ANALYSIS. 




Fig. i. 
Ammonium Platinic Chlorid. 




Fig. 3. 
Potassium Platinic Chlorid. 





Fig. 2. 
Ammonium Phosphomolybdate. 
No. 3 and No. 7 Leitz Objective. 




Fig. 4. 
Cocain and Potassium Permanganate. 




Fig. 5. 
Tri-brom-phenol. 



Fig. 6. 

Morphin. 



PLATE IV.— MICROCHEMICAL ANALYSIS. 




Fig. i. 
Morphin and Marine's Reagent. 




Fig. 3- 
Cocain with Tin Chlorid. 





Fig. 2. 
Magnesium Ammonium Phosphate. 




Fig. 4- 
Chloretone and Sodium Hypochlorite. 




Fig. 5. 
Palmitic Acid. 



Fig. 6. 
Uranyl Sodium Acetate* 



METHODS 163 

13. Crystals formed from morphin and Marine's reagent 
(Plate IV, Fig. 1). 

14. Crystals formed from chloretone and sodium hypo- 
chlorite (Plate IV, Fig. 4.) 

The list may be extended to include the crystals produced 
by various alkaloidal salts with the common reagents, also sub- 
stances usually employed in the manufacture of the various 
dental preparations. 



CHAPTER XIX. 
LOCAL ANESTHETICS. 

In considering the chemistry of local anaesthetics we may 
divide them into two classes as follows : 

First. Those of definite or well-known composition, and 

Second. Preparations of a proprietary nature, the compo- 
sition of which is always problematical. 

In the first class will be found cocain, eucain, tropacocain, 
acoin, ethyl chlorid, etc., which will be later alphabetically 
considered. The second class contains a large number of prep- 
arations of all degrees of value, among them some of exceeding 
merit and largely used, others of doubtful worth, some worth- 
less if not dangerous. Many of the preparations of this class 
contain cocain as the anaesthetic, and frequently a little nitro- 
glycerin as a cardiac stimulant to counteract the depressant 
effect of the alkaloid. Carbolic acid and oil of cloves are also 
frequently used. 

Many of the constituents of this class of anaesthetics may 
readily be identified by the processes of microchemical analysis 
to which previous reference has been made; others may be de- 
tected by special tests, some of which are given under the various 
substances in the following list. This list has been extended to 
include a considerable number of preparations of common 
occurrence. 

Acoin, a synthetic compound (chemically diparanisyl-mono- 

7(NC 6 H 4 OCH 3 ) 2 \ \ 
phenetyl-guanidine hydrochlorid, C HC1 1 sol- 

\(NC 6 H 4 OC 2 Hb)/ / 
uble in both alcohol and water. Strongly antiseptic and a 
valuable anaesthetic, especially in conjunction with cocain. 

164 



LOCAL ANESTHETICS 165 

Acoin should be used only in solution and this should be kept 
in a dark place. 

Adrenalin, a valuable haemostatic and frequently used in con- 
junction with dental anaesthetics, is the active principle of the 
suprarenal gland or capsule. It occurs as very small white 
crystals which are not very stable and only slightly soluble 
in water, hence the article is usually sold in solution with sodium 
chlorid, according to the following formula taken from a com- 
mercial sample: 

Adrenalin chlorid, 1 part; normal sodium chlorid solution 
(with 0.5% chloretone,) 1000 parts. This solution is usually 
diluted with the normal (0.6%) salt solution. According to the 
Druggists' Circular, preparations similar to the above are also 
marketed under the names of adrenol, adnephrin, hemostatin, 
supraredalin, etc. 

Alypin. — Benzoyl - dimethylamino - methyl - dime thylami no- 
butane hydrochlorid, white crystalline, hygroscopic, melts at 
169 C. Soluble in water and alcohol. 

Alypin can be sterilized without decomposition, is not half 
so poisonous as cocain and is cheaper. Is used in 2% solution. 
Solution should be freshly made and prolonged boiling avoided. 
Sometimes used with adrenalin. (Cosmos, 1908, p. 889). 

Alypin nitrate occurs as a white, crystalline powder melting 
at 159 C, readily soluble in ether. Mfrs.: Farbenfabriken of 
Elberfeld, Elberfeld (Germany) and New York. (Mod. Mat. 
Med., page 21). 

Ammonium birluorid is strongly recommended as a solvent 
for tartar by Dr. Joseph Head of Philadelphia. In Items of 
Interest, Vol. 31, page 174, Dr. Head gives the following method 
for its preparation. Hydrofluoric acid is neutralized with am- 
monium carbonate, the solution filtered and evaporated to half 
its bulk, the original volume restored by adding more hydro- 
fluoric acid and then the resulting mixture is again concentrated 
to half its volume by evaporation. 



166 MICROCHEMICAL ANALYSIS 

Anesthol, or Anaesthol, is a mixture of ethyl chlorid and 
methyl chlorid, used as a local dental anaesthetic. The name is 
also applied to a general anaesthetic given by inhalation and con- 
sisting of a mixture of ethyl chlorid 17 parts, chloroform 35.89 
parts, and ether 47.1 parts. 

Anaestheaine, a local anaesthetic, contains 5 grains of stovain 
to the fluid ounce. 

Argyrol, a protein compound of silver, occurs as dark 
brown crystals containing 30% of Ag. It is easily soluble in 
water. It does not precipitate chlorin nor coagulate albumin, 
and is recommended for use in place of ordinary silver 
nitrate. 

Aristol is given by the U. S. D. as a synonym for dithymol- 
diiodid which contains 45% of iodin and is used as an anti- 
septic similarly to iodoform. 

Atropin, an alkaloid obtained from belladonna, usually used 
combined with sulphuric acid, (CuH^NOs^H^SC^; the alkaloid 
is only sparingly soluble in water but the sulphate is easily solu- 
ble, dissolving in about one half part of water at ordinary 
temperature. A 1% solution is said to produce complete insen- 
sibility of the nerves in cases in which an artificial tooth is 
inserted in a living root. (U. S. D., page 249.) 

Tests. — Atropin may be separated from a local anaesthetic 
by first rendering the mixture alkaline with ammonia and 
shaking with chloroform. Upon evaporation of the chloro- 
form solution on a watch-glass the resulting residue may be 
tested by adding a drop or two of sulphuric acid and a trace of 
potassium bichromate and a little water. The odor of bitter 
almonds is produced. A more conclusive test is to convert the 
alkaloid, which has been dissolved by the chloroform, into a salt 
by the addition of a few drops of acetic acid, evaporating to 
complete dryness, taking up in a few drops of distilled water 
and placing one or two drops of this solution in the eye of a 
cat, when, if atropin is present, a dilation of the pupil occurs 






LOCAL ANAESTHETICS 1 67 

in from fifteen minutes to an hour and a half, according to 
amount present. 

Borax. — Sodium tetraborate, Na 2 B 4 7 , is used in antiseptic 
solutions and may be detected as follows: evaporate a little of 
the solution to dryness, add a little HC1, evaporate to dryness 
a second time, then add a very dilute HC1 solution containing 
tincture turmeric. Upon drying this mixture a beautiful pink 
color appears. If much organic matter is present it may be 
burned off in the Bunsen flame before the addition of any acid. 

Carbolic Acid. — See Phenol. 

Chloral Hydrate, CC1 3 CH0.H 2 0, a crystalline solid com- 
posed of trichloraldehyd or chloral with one molecule of water,, 
(U. S. P.) easily soluble in water, may become with alcohol a. 
chloral alcoholate comparatively insoluble in water. 

Tests. — Chloral may be detected by adding to the sus- 
pected mixture a few cubic centimeters of fairly strong alco- 
holic solution of KOH or NaOH with one drop of aniline oil and 
heating, when isobenzonitril is produced, which has a peculiarly 
disagreeable and characteristic odor. This test is also given 
by chloroform, which is produced by heating chloral hydrate 
with caustic alkali. If more than traces of chloral are present 
this latter reaction may be a sufficient test. 

Chloretone, CC1 3 C0H(CH 3 ) 2 , is the commercial name of 
acetone-chloroform or tertiary trichlorbutyl alcohol. Made 
from chloroform, acetone, and an alkali, and occurs as small 
white crystals, with taste and odor like camphor. It is 
dissolved by alcohol and glycerin and to a slight extent by 
water. 

Tests. — A convenient microchemical test for chloretone 
devised by Dr. Niles, Harvard Dental School, '06, consists 
simply of treatment with a solution of hypochlorite of sodium. 
A precipitate is at once formed of a coarsely branching character 
which thus far seems to be characteristic of chloretone solutions 
(Plate IV, Fig. 4). 



1 68 MICROCHEMICAL ANALYSIS 

Chloroform, trichlorme thane, CHC1 3 , prepared by action of 
chlorinated lime on acetone. Chloroform is a heavy colorless 
liquid with a specific gravity of 1.490 at 15 C. Is very 
volatile and used as a solvent for gutta-percha, caoutchouc, 
many vegetable balsams, camphor, iodin, bromin, and chlorin; 
it also dissolves sulphur and phosphorus to a limited 
extent. 

Tests. — It may be detected by its odor, when heated, or by 
the isobenzonitril test to which reference has been made under 
chloral hydrate. 

Cocain is the alkaloid obtained from erythroxylon coca. 
The hydrochlorate, Ci 7 H 2 iN0 4 HCl, is the salt most usually 
employed. This is easily soluble in water and very largely 
used as a dental anaesthetic in a 1 or 2 per cent solution. 

Tests. — Cocain solutions respond to the usual alkaloidal 
reagents. With 1% solution potassium permanganate gives 
pink plates in form resembling cholesterin (Plate III, Fig. 4) 
in form but not in color. 

Dilute cocain solution with picric acid gives a yellow pre- 
cipitate which becomes crystalline on standing. Quite char- 
acteristic crystals also may be obtained from dilute cocain 
solutions and stannous chlorid in the presence of free HC1 
(Plate IV, Fig. 3). 

Creosote. — A mixture of phenols derived from the destruc- 
tive distillation of wood tar. It is a heavy oily liquid acting 
when pure as an escharotic. It is analogous in many respects 
to carbolic acid and may be used for similar purposes. To 
distinguish between creosote and carbolic acid, boil with nitric 
acid until red fumes are no longer given off. Carbolic acid will 
give yellow crystalline deposit; creosote will not. An alco- 
holic solution of creosote is colored emerald green by an alcoholic 
solution of ferric chlorid. Phenol is colored blue. 

Cresol is the next higher homologue to phenol, having a 
formula C 6 H 4 CH 3 OH, boiling at 198 C. It is largely used, 






LOCAL ANESTHETICS 169 

usually together with allied compounds from coal-tar, as anti- 
septic and disinfectant solutions. 

Ektogan. — Peroxid of zinc, Zn0 2 , designed for external 
use (London, July 9, 1904). 

Ethyl Chlorid monochlore thane, C 2 H 5 C1. This is a gaseous 
substance at ordinary temperature, but when used as a dental 
anaesthetic it is compressed to a colorless liquid which has a 
specific gravity of 0.918 at 8° C, is highly inflammable and usu- 
ally sold in sealed glass tubes of from 10 to 30 grams each. 

p-Eucain is the hydrochlorate of benzoylvinyldiacetone- 
alkamine, and occurs as a white, neutral powder, soluble in 
about 30 parts of cold water. It is used like cocain as a local 
anaesthetic, and is claimed to be less toxic, and sterilizable by 
boiling without danger of decomposition. It is usually applied 
in from 1 to 5 per cent solutions, which are conveniently prepared 
in a test-tube with boiling water. It is also marketed in the 
form of i|- and 5-grain tablets. (Druggists' Circular.) 

Eucain Lactate. — " Eucain lactate is used in 2 to 5 per cent 
solution as a local anaesthetic in ophthalmic and dental prac- 
tice and in 10 to 15 per cent solution when used in the nose or 
ear." (Review of American Chemical Research, page 97, 1905). 

Eudrenin is a local anaesthetic marketed in capsules of 
0.5 c.c. containing 1/12 grain of eucaine and 1/4000 grain of 
adrenalin hydrochlorid. It is used as a local anaesthetic, chiefly 
in dentistry. The contents of one or two capsules, according 
to the number of teeth to be extracted, are injected into the 
gums ten minutes before extraction. Mfrs. : Parke, Davis & 
Co., Detroit, Mich. (Mod. Mat. Med., page 147.) 

Eugenol, Ci Hi 2 O 2 , synthetical oil of cloves. Eugenol is mis- 
cible with alcohol in all proportions. Exposure to air thickens 
and darkens it. Should be kept in well-stoppered amber-colored 
bottles (U. S. D.). 

Europhen — recommended by Dr. J. P. Buckley as a sub- 
stitute for iodoform (Dental Review, Vol. 21, page 1284). 



170 MICROCHEMICAL ANALYSIS 

Di-iso-butyl-cresol is described as a bulky yellow powder of faint 
saffron odor and containing 28% of iodin. (Mod. Mat. Med., 
page 152.) 

Formalin, Formol, Formin, etc., are commercial names 
for a 40% aqueous solution of formaldehyd, HCHO, prepared 
by the partial oxidation of methyl alcohol. Formalin is a 
powerful disinfectant very generally used. (For test see page 
201, Exp. 62.) 

Glycerol is a triatomic alcohol, C 3 H 5 (OH) 3 , a colorless liquid 
of syrupy consistence and sweetish taste, specific gravity 1.250 
at 1 5 C. It is easily soluble in either water or alcohol. 

Tests. — Upon heating strongly it is decomposed, giving 
off odor of acrolein, which is usually sufficient for its identi- 
fication. A further test may be made by moistening a borax 
bead on a platinum wire with the suspected solution (after con- 
centration) and holding in a non-luminous flame, to which it 
will give a deep-green color which does not persist. Glycerol 
when present is apt to interfere with characteristic crystalliza- 
tion of many precipitates. 

Grants Solution, Kuhne's modification, contains 2 grams 
of iodin, and 4 grams potassium iodid in 100 c.c. of water. 

Gutta-percha. The name signifies scraps of gum. It is ob- 
tained as a milky exudate from a number of tropical trees. It 
is soluble in ether, chloroform, carbon disulphid, toluene and, 
petroleum ether. It may be freed from impurities by shaking 
the solution with calcium sulphate, which will mechanically carry 
coloring matter and other impurities with it as it slowly settles 
out from the mixture. It is not soluble in alcohol or in water. 

Heroin is a diacetic ester of morphin. It is usually ob- 
tained as the hydrochlorid and occurs as a white powder, solu- 
ble in two parts of water. Its action is similar to that of morphin ; 
it answers to the usual tests for morphin, but may be distinguished 
from it by the fact that it will yield acetic ether upon heating 
with alcohol and sulphuric acid. 



LOCAL ANESTHETICS 171 

Hopogan (also known as biogen) is a peroxid of magnesium, 
Mg0 2 , recommended as a non-poisonous and non-astringent 
intestinal germicide. 

Hydrogen Peroxid, or dioxid, H 2 2 , is, when pure, a syrupy 
liquid without odor or color. It is sold under various trade 
names in aqueous solution containing about 3% and yielding 
upon decomposition about 10 volumes of oxygen gas. It is 
used also as an escharotic in etherial solutions containing 25 to 
50 per cent H 2 2 . Peroxid solutions may be concentrated by 
heat without decomposition if kept perfectly free from dirt or 
traces of organic matter. It is readily prepared by treatment of 
metallic peroxids, as Ba0 2 with dilute acids. 

Ba0 2 + H 2 S0 4 = BaS0 4 + H 2 2 
or Ba0 2 + H 2 + C0 2 = BaC0 3 + H 2 2 . 

This latter reaction has the advantage of producing an insolu- 
ble barium compound and at the same time introducing no 
objectionable acid. The peroxids of sodium, calcium, magne- 
sium, and zinc may also be used; Zn0 2 , however, is compara- 
tively expensive and used in powder form as an antiseptic 
dressing rather than as a source of H 2 2 . Na 2 2 is valuable as 
a bleaching agent, because for this purpose an alkaline solution 
is required and the solution of Na 2 2 in water produces both 
alkali and H 2 2 according to the following reaction: 

Na 2 2 + 2 H 2 = 2 NaOH + H 2 2 . 

Sodium perborate (page 175), also sold as euzone, is a powder 
advertised to produce H 2 2 in water. Commercial H 2 2 solu- 
tions are usually acid in reaction, as such solutions are more 
stable than if neutral or alkaline. 

Lugol's Caustic Iodin is made of iodin and potassium 
iodid, 1 part of each dissolved in 2 parts of water. 

LugoPs Iodin Solution contains 5 grams of odin and 10 
grams of potassium iodid dissolved in sufficient water to make 
100 grams. 



172 MICROCIIEMICAL ANALYSIS 

Menthol is the stearopten obtained from the oil of pepper- 
mint. It is a volatile crystalline substance having a formula 
C6H9OHCH3C3H7. Menthol is but slightly soluble in water 
but freely soluble in alcohol, ether, chloroform, or glacial acetic 
acid. The presence of menthol may usually be detected by 
its odor. If the odor should be suggestive but not distinctive 
it is well to place a little of the substance on a filter-paper, rub 
it between the thumb and finger, thereby obtaining a ''fractional 
evaporation," when the more easily volatile substance will pass 
off first, thus producing a partial separation of substances. 

Mercuric Chlorid, corrosive sublimate, HgCl 2j is soluble in 
about 16 parts of water and 3 parts of alcohol. It is a power- 
ful antiseptic, in aqueous solution i/iqoo to 1/5000, but should 
never be used in mouth-washes. 

Tests. — A drop of the suspected solution with a trace of 
potassium iodid will give a red precipitate of mercuric iodid 
soluble in excess of either reagent. With lime-water or fixed 
alkaline hydroxids a black precipitate is produced. A drop of 
mercurial solution placed on a bright copper plate will leave 
a tarnished spot due to the reduction of the mercuric salt and 
subsequent amalgamation of the metal. 

Methethyl. — Ethyl chlorid mixed with a little methyl chlorid 
and chloroform is said to be the composition of a local anaes- 
thetic sold under the name of methethyl (U. S. D.). 

Methyl Chlorid, CH 3 C1, is a colorless gas which condenses to 
a liquid at 23 C. Methyl chlorid is easily soluble in alcohol, 
somewhat in water, and is used in a similar manner to ethyl 
chlorid. 

Morphin, C17H19NO3, alkaloid from opium. Solutions for 
use are made from the sulphate, hydrochlorate, or acetate. The 
alkaloid itself is insoluble in water; its salts are easily soluble. 

Morphin may be separated from solutions containing it by 
making the solution alkalin with ammonia, and shaking out 
the precipitated alkaloid with warm amyl alcohol. Upon 



LOCAL AXJESTHETICS 173 

evaporation of the alcohol the residue may be tested with 
Frohde"s reagent (sodium molybdate. 1%, in strong sulphuric 
acidi. The color obtained should be a violet, changing usually 
to brown; a pure blue color is not distinctive for morphin. If 
the morphin solution is of sufficient strength the addition of am- 
monia will produce minute crystals of the alkaloid as shown on 
Plate III. Fig. 6. Dental anaesthetics containing morphin will 
give precipitates with the usual alkaloidal reagents. Marine's 
reagent I Cdl ; gives crystals represented on Plate IV, Fig. 1. 

Nirvanin, hydrochlorid of diethyl-glycocoU-^-amino-o-oxy- 
benzoic-methylester. of the formula 

(CH 2 N) = (C 2 H 5 ^HC1 
(CO.NH.C 6 JL; OH COOCH 3 . 

White prisms soluble in water and in alcohol, melt at 185 C. 
violet reaction with ferric chlorid. 

Nitroglycerin, C3H51NO3V is used as a cardiac stimulant 
in alcoholic solution, the U. S. P. Spiritus Glonoini. containing 
1% by weight of the substance. 

Novocain, discovered by Uhlf elder and Einhorn. is a hydro- 
chlorid /?-arnmobenzoyl-diethylamino-ethanol. It occurs as thin 
colorless needles; melts at 156 C, soluble in 1 part H 2 and 
30 parts alcohol. It is seven times less toxic than cocain. and 
three times less toxic than s to vain. It can be sterilized by 
boiling, and is used in 1 2 to 2 r c solution often with adrenalin 
1 1000. (Mod. Mat. Med., page 275). 

Novocain, if intended to represent a solution which is 
isotonic with the blood corpuscles, must be dissolved in a 0.92 
per cent sodium chlorid solution. (Dental Cosmos, 1910. page 
605.) 

Oil of Cloves, oil of Gaultheria. and other essential oils may 
be detected by the same process of fractional evaporation as 
suggested for menthol. In testing for the presence of any sub- 



174 MICROCHEMICAL ANALYSIS 

stance by its odor, it is usually necessary to make a comparative 
test on known samples using the same methods. 

Orthof orm, C 6 H 3 OH (NH 2 ) COOCH 3 , methylparaamino- 
metaoxybenzoate, used as an anaesthetic and antiseptic, is 
without odor, color, or taste, is slightly soluble in water and 
easily soluble in alcohol or ether. 

Phenol. — Carbolic Acid. C 6 H 5 OH, obtained from the de- 
structive distillation of coal-tar. A light oily liquid of specific 
gravity of 0.94-0.99. Carbolic acid is usually obtained as a 
white crystalline mass soluble in 20 parts of water. The pure 
acid turns pink with age, but does not suffer deterioration on 
account of this change of color. The addition of from 5 to 8 
per cent of water will cause liquefaction of the crystals and the 
preparation becomes permanently liquid. It is easily soluble 
in glycerol and strong solutions may thus be prepared. Car- 
bolic acid is sometimes added to local anaesthetics with the in- 
tent of rendering the solution sterile, but as shown by Dr. 
Endelman (Dental Cosmos Vol. 45, page 44) it would be neces- 
sary, in order to prevent the development of micro-organisms, to 
add the acid in proportion that would render the solution unfit 
for hypodermic purposes. 

Tests. — Phenol may be detected in the majority of prepara- 
tions by the addition of bromin-water, which gives white crys- 
tals of tribromphenol (see Plate III, Fig. 5). 

Phenol Compound — Dr. Buckley's formula for treatment of 
root canals — menthol 1.3 grams, thymol 2.6 grams and phenol 
12 c.c. 

Potassium Hydroxid, KOH, gives an alkaline reaction to 
litmus paper and may be detected by the ordinary methods of 
inorganic analysis. 

Rhigolene is a light inflammable liquid obtained from 
petroleum, boiling at about 18 C, used as a spray for the 
production of low temperature, similarly to methyl or ethyl 
chlorid. It is readily inflammable, and the vapor, mixed with 



LOCAL ANESTHETICS 175 

certain proportions of air is explosive. It should be kept in a 
cool place. 

Saccharin — the commercial name of benzosulphinid, a 
derivative of toluene — is a white crystalline powder 300 times 
sweeter than cane sugar and is used in mouth- washes, tooth- 
paste, etc., as a flavor and an antiseptic. 

Silver Nitrate, AgN0 3 , crystallizes in colorless plates 
without water of crystallization; used as an antiseptic, dis- 
infectant, or escharotic. It is freely soluble in water and may 
be detected by the ordinary methods of qualitative analysis 
(page 19). 

Sodium Chlorid, NaCl, is a constituent of many prepa- 
rations designed to be used hypodermically. Experience has 
proved the value of such addition; perhaps the reason for its 
desirability is given by Dr. G. Mahe, of Paris, in the Dental 
Cosmos for September, 1903, in the statement that sodium 
chlorid added in excess to a toxic substance diminishes its 
toxicity by one half, and this has been demonstrated particu- 
larly with cocain. 

Sodium Perborate, a powder said to have the composition 
NaB0 3 .4 H 2 0, which will furnish 10% of available oxygen and 
produce H2O2 with water; very stable and recommended as a 
bleach-powder. 

Sodium perborate may be made * by thoroughly mixing 
78 grams Na 2 and 248 grams of crystallized H3BO3 and stirring 
the mixture gradually into 2 liters of cold H 2 0. The sodium 
perborate, Na 2 B 4 8 +10 H 2 0, is formed spontaneously and 
settles out from the solution as a white crystalline powder. 
Its solubility is increased by addition of weak organic acids, 
citric or tartaric. 

Sodium Peroxid, Na 2 2 . — A white powder easily soluble in 
water, usually with evolution of more or less oxygen and forma- 
tion of hydrogen dioxid. 

* Dental Cosmos, Nov., 1905, page 1381. 



176 MICROCHEMICAL ANALYSIS 

Somnof orm. — A general anaesthetic administered in manner 
similar to chloroform; introduced by Dr. Rolland, of Bordeaux; 
consists of 60% ethyl chlorid, 35% ethyl bromid, and 5% 
methyl bromid. ( Dental Cosmos, Vol. XL VII, page 236.) 

Stovain. — Benzoylethyldimethyl-aminopropanol hydrochlo- 
ride C14H21O2N.HCI, closely related to alypin, small shining 
scales freely soluble in alcohol or water. Incompatible with 
alkalies and all alkaloidal reagents. Can be sterilized by boil- 
ing. (Mod. Mat. Med., 2nd edition.) 

It melts at 17 5 C, is very soluble in H 2 0, and gives reaction 
similar to cocain, which is also a benzoyl derivative. (U. S. D., 
page 1 66 1.) 

It is less powerful than cocain and physiologically incom- 
patible with adrenalin. (Dental Cosmos, 1905, page 146.) 

Tannic Acid, or tannin, sometimes called gallo tannic acid, 
is an astringent organic acid obtained from nutgalls. It may 
be obtained as crystals carrying 2 molecules of water, 
HCuHgOg 2 H 2 0. Tannic acid is a white or slightly yellowish 
powder soluble in about one part of water or 0.6 part alcohol. 
It is used as an alkaloidal precipitate, also in astringent washes. 
It may be detected by the addition of ferric solutions which 
form with it a black tamiate of iron of the nature of ink. 

Thymol, C 6 H 3 (CIl3)(OH)(C3H7) 1:3:4: a phenol, occurring 
in volatile oils of thymus vulgaris (Linne). Melts at 44°C; 
sparingly soluble in water, easily in alcohol and ether. 

Tests. — It may usually be detected by its odor or by dis- 
solving a small crystal in 1 c.c. of glacial acetic acid, when if 
6 drops of sulphuric acid and 1 drop of nitric acid be added, 
the liquid will assume a deep bluish-green color. (U.S.D.) 

Thymophen, a mixture of equal parts of thymol and 
phenol. 

Trichloracetic Acid occurs as deliquescent crystals, readily 
soluble in water. Distils at 195 C. and is a powerful caustic. 
Dilute solutions are recommended for treatment of pyorrhoea. 



LOCAL ANESTHETICS 



177 



Tropa-cocain is an alkaloid originally isolated by Giesel 
from the leaves of the small-leaved coca-plant of Java and intro- 
duced by Arthur P. Chadbourne, Harvard Medical School. 
Used hypodermically in normal salt solution. It is probably 
superior to cocain, but rather more expensive. It is obtained 
as an oil which, when quite dry, solidifies in radiating crystals, 
melting at 49 C. It is easily soluble in alcohol. 

Laboratory Exercises XL VII to XLIX. 

A number of commercial mouth-washes and local anaesthetics 
will be given to the class for identification, the object being to 
familiarize the student with the more easily made tests for the 
principal ingredients of these preparations. Complete analysis 
will rarely be attempted. The following table, taken from the 
Druggist's Circular of June, 19 10, may be helpful. 

DIFFERENTIATION OF COCAIN AND ITS SUBSTITUTES. 





Iodin potassium 
iodid. 


Bromin water. 


Sodium hydroxid. 


Potassium per- 
manganate. 


Eucain — a. 


Yellow-maroon 


Yellow precipitate, 


White precipitate, 


Violet precipitate, 




precipitate, 


soluble on heat- 


insoluble in ex- 


blackening 




soluble on 


ing. 


cess and on boil- 


quickly. 




boiling. 




ing. 




Eucain — b. 


Deep-red pre- 


Yellow precipitate, 


White precipitate, 


No precipitate 




cipitate, solu- 


slightly soluble 


insoluble in ex- 


immediately; 




ble on boiling. 


on heating, re- 


cess and on 


color persists 






precipitated 


boiling. 


for a day. 






white on boiling. 






Cocain 


Yellow-maroon 


Yellow precipitate, 


White precipitate, 


Violet precipitate, 




precipitate, 


soluble on heat- 


insoluble in ex- 


color persists 




soluble on 


ing. 


cess and on 


for one hour, 




boiling. 




boiling. 


then deposits 
Mn0 2 . 


Novocain 


Deep-red pre- 


Yellow precipitate, 


White precipitate, 


Violet precipitate, 




cipitate, solu- 


soluble on heat- 


insoluble in ex- 


blackening 




ble on boiling. 


ing. 


cess and on boil- 


quickly. 


Stovain 


Deep-red pre- 


Yellow precipitate, 


ing. 
White precipitate, 


Violet precipitate, 




cipitate, solu- 


soluble on heat- 


insoluble in ex- 


blackening al- 




ble on boiling. 


ing. 


cess; aromatic 
odor on boiling. 


most immedi- 
ately. 


Nirvanin 


Deep-red pre- 


Yellow precipitate, 


Precipitate very 


Precipitate, first 




cipitate, solu- 


soluble on heat- 


soluble in excess 


maroon, then 




ble on boiling. 


ing, but the 
liquid becomes 
red and gives an 
agreeable fruity 
odor. 


of the reagent. 


brown. 


Alypin 


Yellow-maroon 


Yellow precipitate, 


White precipitate, 
insoluble in ex- 


Bluish-violet pre- 




precipitate, in- 


soluble on gentle 


cipitate, slowly 




soluble on 


heating. 


cess and on boil- 


blackening. 




boiling; orange 




ing. 






red deposit. 









CHAPTER XX. 
TEETH AND TARTAR. 

The chemical examination of teeth and tartar, while coming 
more properly under the head of physiological chemistry, will 
be considered in part in this place, as the tests made, especially 
on tartar, are practically all microchemical. The composition 
of the cement is practically that of true bone, the dentine and 
enamel differing principally in the proportion of organic matter 
which they contain. In all of these the presence of lime, phos- 
phoric acid, carbonic acid, and traces of magnesium and calcium 
fluorid may be demonstrated. The tartar contains a greater 
proportion of carbonic acid, less calcium phosphate, and much 
less organic matter than the teeth, taken as a whole, or than 
dentine, but about the same as enamel. According to Berzelius, 
sodium chlorid and sodium carbonate may also be found. 

The composition of the different parts of the tooth sub- 
stance has been given as follows : 

MattS Ash - Ca 3(PO*)2. MgHP0 4 . CaCO,. 

Dentine 23.2 76.8 70.3 4.3 2.2 

Cement 32.9 67.1 60.7 1.2 2.9 

Enamel 3.1 96 . 9 90 . 5 traces 2 . 2 

Also traces of magnesium carbonate, calcium sulphate, fluorids, 
and chlorids. An increase in the percentage of calcium phos- 
phate of fluorid increases the hardness of the tooth, while an 
increase of calcium carbonate decreases the hardness. 

Potassium sulphocyanate, ferric phosphate, sulphites, and 
uric acid have been found in tartar, as additional chemical 
constituents, while after the solution of the mineral matter 

178 



TEETH AND TARTAR 1 79 

the presence of epithelium cells, mucus, and the leptothrix may 
be demonstrated by the microscope. 

According to Vergness, Du tartre dentaire, quoted by Gamgee, 
the tartar from incisor teeth and that from molars show decided 
difference in their content of iron and calcium phosphates, the 
analysis being as follows: 

Tartar of Incisors. Tartar of Molars. 

Calcium phosphate 63.88-62.56 55. 11-62. 12 

Calcium carbonate 8.48-8.12 7.36-8.01 

Phosphate of iron 2.72-0.82 12.74- 4.01 

Silica 0.21- 0.21 0.37-0.38 

Alkaline salts 0.21- 0.14 0.37-0.31 

Organic matter 24.99-27.98 24.40-24.01 

Tartar from patients with pyorrhoea has been found to 
contain oxalates and urates, not necessasily together, but often 
one or the other. The deficient oxidation and high acidity 
usually occurring in such cases is conducive to the production 
of large amounts of oxalic or uric acids (most generally the 
latter) whether these substances have etiological relations to 
pyorrhoea or not. 

Lactic and other organic acids have been found in minute 
quantities in tartar, but these as well as the qualitative tests for 
urates will be considered more in detail under the Chemistry 
of Saliva. 

Analysis or Teeth and Tartar. 

The substance for analysis should be reduced to a moder- 
ately fine powder by crushing in a mortar and a fair sample 
of the whole taken for each test. 

Moisture may be detected by the closed-tube test (page 99) 
and may be determined by accurately weighing out 1 gram 
of the substance in a counterpoised platinum dish or crucible 
and drying at ioo° C. to constant weight. 

Inorganic Matter may be determined by careful ignition 
of dried substance; raise the temperature slowly till full red heat 
is reached; cool in a desiccator and weigh. 

Organic Matter may be ascertained by difference. 



l8o MICROCHEMICAL ANALYSIS 

Lactates and other organic acids may be detected by careful 
crystallization and examination with the micropolariscope. 

The several inorganic constituents may be demonstrated 
as follows: 

Phosphoric Acid. — Dissolve a little of the powdered sub- 
stance in dilute HNO3; then to a few drops of the clear solution 
add an excess of ammonium molybdate in nitric acid. A yellow 
crystalline precipitate of ammonium phosphomolybdate will 
separate. Avoid heating above 6o° C, as the ammonium 
molybdate may decompose and precipitate a yellow oxid of 
molybdenum. 

Carbonic Acid may be detected by liberation of C0 2 and 
passing the gas into lime-water as described on page 87 or 
with closed tube and drop of baryta- water, page 99. 

Chlorin may be detected in the dilute nitric acid solution by 
the usual silver nitrate test. 

Calcium and Magnesium may be separated and identified 
by the usual methods of analysis in the presence of phosphates. 

Test for calcium and magnesium as follows: Add to the 
HO solution an excess of ammonia; calcium phosphate and 
magnesium phosphate are precipitated, white. Filter, and to 
the nitrate add ammonium oxalate; a white precipitate shows 
lime, not as phosphate. Wash the precipitate produced by 
NH4OH, dissolve in dilute HC1, and add Fe 2 Cl 6 carefully till 
a drop of the solution gives, when mixed with a drop of NH 4 OH, 
a yellowish precipitate. Nearly neutralize with Na 2 C0 3 and 
add BaC0 3 , which precipitates ferric phosphate. Filter, heat 
the filtrate, precipitate the barium with dilute sulphuric acid, 
and filter again. From the filtrate calcium is precipitated as 
white calcium oxalate by making it alkaline with NH 4 OH and 
adding (NH 4 ) 2 C 2 4 as long as a precipitate is formed. Filter 
and add to the filtrate sodium phosphate, which precipitates 
magnesium as ammonio-magnesium phosphate, white. 

Laboratory Exercises No. L will consist of the examina- 
tion by microchemical methods of one or more samples of tartar. 



PART V. 
ORGANIC CHEMISTRY. 

CHAPTER XXI. 
THE HYDROCARBONS AND SUBSTITUTION PRODUCTS. 

Our work up to this point has been confined to inorganic 
chemistry excepting a few microchemical tests for organic 
substances. 

We are now to consider briefly the organic compounds which 
will serve as a basis for the intelligent study of physiological 
chemistry, and also some which are of peculiar interest in 
dentistry. 

We shall touch but lightly on some of the subdivisions of the 
subject and take up a little organic chemistry proper, a little 
physiological chemistry, a little pathological chemistry, and 
from it all pick out such facts as may help us to a better under- 
standing of the problems of dentistry. 

As in many other departments of science, absolute rules for 
classification are impracticable; yet we may consider in a 
general way that the organic compounds are those containing 
carbon as a molecular constituent. The old conception that the 
organic compound must have been produced by a vital process 
of some sort (animal or vegetable) is of little value unless we 
confine our thought to substances found in nature only. 

The compounds of carbon are practically innumerable and 
very widely distributed, constituting the great bulk (aside from 
water) of all vegetable or animal substances. 

181 



182 ORGANIC CHEMISTRY 

The carbon compounds contain the elements of C and H, 
and when these two only are present they are hydrocarbons. 
They more frequently contain C, H, and O, and when the H 
and O are present in the proportions in which they occur in 
water, the compound is a carbohydrate (with exceptions). 

In the chemistry of the animal body the majority of sub- 
stances which we meet contain C, H, O, and N and often in 
addition S or P. Many other elements, notably the halogens, 
and often the metals, may be found in organic compounds. 

The question of its composition is then the first one pre- 
senting itself in the consideration of an organic substance. 

The analysis of organic bodies may be made from two dis- 
tinct standpoints: first, to determine the various substances 
which may be separated from a given organized body, as from 
some part of a plant; secondly, to determine the constituent 
elements of one of the substances so separated. 

As an example of the first sort of analysis, we may find in a 
potato a certain basic principle (alkaloid), more or less water, 
and considerable starch. These may be called proximate prin- 
ciples, and the separation of them would be proximate analysis, 
while the second sort of analysis determines the composition of 
the starch molecule and is known as ultimate analysis. 

Qualitative Tests. 

Carbon. — The presence of this element may be shown by 
the "carbonization" obtained in the preliminary test, as given 
on page 98. 

Hydrogen shows itself by the production of moisture in 
these same tests. 

Nitrogen may or may not be indicated by the preliminary 
test. It may be detected with certainty by either of the 
following methods : 

(a) Conversion into a cyanogen compound; 

A small piece of thoroughly dried albumen together with 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 185 

a little metallic potassium, is placed in a matrass, such as is 
described on page 28, and heated to redness for a few minutes. 
(Metallic sodium will work as well in most cases.) An alkali 
cyanide, which may be dissolved in water after breaking the 
tube, is formed, and by addition of a little yellow ammonium 
sulphid and evaporation to dryness on a water-bath will be 
changed to sulphocyanate, NH 4 CNS. If the dry residue is taken 
up with dilute HC1, filtered, and tested with a drop of ferric 
chlorid solution, the presence of the sulphocyanate is at once 
shown by the red color produced. 

(b) Conversion into free ammonia. 

Almost any nitrogenous substance may be made to evolve 
ammonia-gas by simply heating in a test-tube with several times 
its bulk of soda-lime. Test for NH 3 by moistened red litmus 
paper or by odor. (This test is known as that of Wohler, also 
of Will and Varr entrap.) 

The Kjeldahl or moist combustion process is much employed 
as a quantitative method but may be used qualitatively as 
follows: The substance is heated in an ignition- tube with con- 
centrated sulphuric acid till a clear (not necessarily color- 
less) solution is obtained. The mixture is cooled, diluted with 
water, an excess of caustic soda added, and heat applied when 
NH 3 is evolved, which may be detected by litmus paper or by 
odor. 

Sulphur and Phosphorus are' first completely oxidized 
either by fusion of the substance with alkali nitrate and car- 
bonate, or by treatment in the wet way with fuming HN0 3 
or mixture of KC10 3 and HC1. The resulting sulphate or phos- 
phate is detected by the usual qualitative methods (page 92). 

A sulphur test may also be made by heating the substance 
with a little concentrated NaOH in the test-tube. A little 
sodium sulphid, which may be detected by dropping onto a 
bright silver coin or by testing with lead acetate solution, will 
thus be formed. 



184 ORGANIC CHEMISTRY 

Halogens. — CI, Br, and I cannot be detected in organic 
combinations by the ordinary qualitative test with AgN0 3 and 
dilute NHO3, but must first be converted into corresponding 
inorganic haloid salts. This may be done by heating the organic 
substance strongly with pure lime, when calcium chlorid, bromid, 
etc., which may be dissolved in water and tested in the usual 
way, will be formed. (See pages 90 and 91.) 

A test for chlorin or iodin may also be made by heating 
with copper oxid on a platinum wire in the Bunsen flame, chlorin 
giving first a blue then a green color to the flame. Iodin gives 
a green only (Beilstein). 

Test for presence of C, H, and S in dried albumen. 

Test for S by the caustic soda test. 

Test for P in casein precipitated from milk. 

Test a few drops of chloroform for the presence of chlorin. 

The Hydrocarbons. 

The hydrocarbons are organic compounds of carbon and 
hydrogen only. The simplest of these is marsh-gas or methane 
(CH 4 ). The molecule of this substance consists of a single 
carbon atom with each of its four points of atomic attraction 
(valence) satisfied by an atom of hydrogen. 

H x /H 
C 

If one of these four atoms of H is replaced by a chlorin atom, 
for instance, we have a substitution product. Its formula will 
be CH3CI, its name monochlormethane or methyl chlorid. If 
two molecules of methyl chlorid are brought together and 
the CI removed by metallic sodium the residual molecules 
(methyl radicals) will unite, forming a new hydrocarbon, as 
follows : 

2 CH3CI + Na 2 = 2 NaCl + C 2 H 6 (ethane). 



THE HYDROCARBONS AXD SUBSTITUTION PRODUCTS 185 

By a similar reaction we may form the third member of 
the series, C 3 H 8 (propane), from ethyl chloric! (C 2 H 5 C1) and 
sodium; the fourth member, butane, C 4 Hi , from propyl chlorid, 
etc. A tabulated list of the first five compounds of this series 
will plainly show their chemical relationship : 

CH 4 , methane or methyl hydrid (CH 3 H). 
C 2 H 6 , ethane or ethyl hydrid (C 2 H 5 H). 
C 3 H 8 , propane or propyl hydrid (C3H7H). 
C4H10, butane or butyl hydrid (C 4 H 9 H). 
C5H12, pentane or amyl hydrid (C 5 HnH). 

Note that the various members of this series differ from one 
another by CH 2 ; that is, each higher compound contains one 
carbon atom and two hydrogen atoms more than its predecessor. 
This holds true through the series, and the compounds of this 
or any such series are termed homologues and the series ho- 
mologous series. Xote further that any member of this series 
(which is known as the paraffin series) may be represented by 
the general formula C n H 2n+2 . This likewise holds true through- 
out the series, and a compound having sixty carbon atoms will 
have a formula of C 6 oHi 22 . The first four hydrocarbons of 
this series are gaseous at ordinary temperatures; from C 5 Hi 2 to 
about Ci 6 H 34 the hydrocarbons are liquid; from Ci 6 H 34 (melt- 
ing at about 18 ) up they are solids. 

Isomers. — When two or more compounds are of exactly 
the same molecular composition in regard to numbers and kind 
of atoms, they are isomeric substances or isomers. 

Thus we may have a normal butane represented graphically 

HHHH 

I I I I 
by H-C-C-C-C-H (C 4 Hi ), then we may have an isomeric or 

I I I I 
HHHH 

isobutane represented by 



lS6 ORGANIC CHEMISTRY 





H 




H H 




\ L/ 


H 


c 


1 


-c; h 


H-C- 


1 


'\ ' 


H 


H N C-H 




\ 




H 



also C4H10, but having different physical and chemical properties 
from the normal compound. The greater the number of carbon 
atoms in the molecule, the more numerous the possible isomers. 

Polymers. — When one compound has a formula which may 
be regarded as a multiple of another, it is said to be a polymer 
of it; thus, paraform, a white crystalline solid, (CH 2 0)3, is a 
polymeric form of the gaseous formaldehyd, CH 2 0. 

The hydrocarbons of the paraffin series are known as straight 
chain or aliphatic hydrocarbons, their graphic formulae consist- 

! i t I 

ing of " chains" of carbon atoms, as butane, -C-C-C-C-, in 

1 1 l 1 
distinction from the closed-chain or cyclic compounds as repre- 
sented by the "benzole-ring" (page 240) carbon nucleus with 
the C atoms united in a continuous closed chain or " cycle." 

The paraffins are called saturated hydrocarbons because 
they are incapable of forming addition products by absorption 
of CI, for instance, without first giving off an equivalent num- 
ber of atoms of H. This is because of the complete " satu- 
ration" or union of every carbon "bond" with some other 
atom.* Paraffin wax and mineral oil are mixtures of saturated 
hydrocarbons and resist chemical action even of strong nitric 
acid or sulphuric acid. 

The natural sources of hydrocarbons of the paraffin series 

* Notice that while addition products of saturated hydrocarbon cannot be 
formed, substitution products are easily possible. See page 184. 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 187 



are natural gas and crude petroleum, 
or rock oil. Many of these hydro- 
carbons exist as such in the petro- 
leum, and some undoubtedly are 
produced by the heat used to effect 
a separation of the various com- 
pounds. This separation is effected 
by distilling the oil in an apparatus 
similar to that pictured in Fig. 15, 
and is known as fractional distillation, 
the different hydrocarbons passing 
over at different temperatures. Sep- 
aration by this method, however, is 
by no means complete, and the 
resulting products are themselves 
mixtures of hydrocarbons, and are 
distinguished by physical depravities 
rather than by chemical composition. 
When crude petroleum is thus 
distilled, the following products are 
obtained : first, rhigoline, which comes 
over at a temperature of 20 to 22 
C; then petroleum ether or benzine 
at from 50 to 6o° C; then gasolene 
or naphtha at about 75 C; then 1 
or 2 unimportant commercial pro- 
ducts, and kerosene or burning oil is 
obtained at 150 to 250 C. Above 
this, we may obtain paraffin oil or 
light lubricating oils; then the heavy 
lubricating or cylinder oils, and from 
the residue we obtain the solid sub- 
stances known as vaseline or petrola- 
tum and paraffin of various degrees 
of hardness. 




Fig. 15. 



1 88 ORGANIC CHEMISTRY 

The first five hydrocarbons of this series we will consider 
somewhat in detail, not only because they are important and 
comparatively common, but also because they serve as types of 
all other compounds of the series and reactions which we study 
with these compounds, or, as a rule, general typical reactions 
which may be produced with other members of the series. 

Methane, CH 4 , occurs as marsh gas in stagnant ponds or 
pools and is a constituent of " fire damp" in coal mines. It is 
a colorless gas, odorless when pure, and very slightly soluble 
in water. It may be prepared artificially by the decomposition 
of anhydrous sodium acetate, with sodium hydroxid and lime. 
See reaction on page 191, Exp. 50. Methane burns in the air 
with the production of carbon dioxid and water 

CH 4 + 2 2 = C0 2 + 2 H 2 0. 

Ethane, C2H6, the second member of the series, occurs natur- 
ally in a solution in crude petroleum, and can be artificially pre- 
pared by the electrolytic decomposition of a saturated solution 
of potassium acetate as follows: 

2 CH3COOK = C 2 H 6 + 2 C0 2 + K 2 . 

The free potassium, of course, decomposes H 2 0, liberat- 
ing hydrogen gas which collects at the negative pole, and, if 
the solution contains sufficient KOH, the C0 2 will be dissolved, 
allowing C 2 H € to collect at the positive pole. 

Ethane may also be made from a haloid derivative of marsh 
gas by the action of metallic sodium; that is, in CH 4 we may 
replace one of the hydrogen atoms with iodin, forming CH 3 I 
of methyl iodid; then by treatment with metallic sodium, the 
following reaction will take place: 

2 CH3I + 2 Na = C 2 H 6 + 2 Nal. 

Ethane is slightly more soluble in water than methane. It 
may be condensed to a liquid at a pressure of 46 atmospheres. 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 189 

Propane, C 3 H 8 , also occurs in petroleum, and can be made by- 
treating a mixture of ethyl iodid and methyl iodid with metallic 
sodium : 

C 2 H 5 I + CH3I + 2 Na = C 3 H 8 + 2 Nal. 

This is a general method for building up hydrocarbon com- 
pounds. Propane at ordinary atmospheric pressure is con- 
densed to liquid at 17 below zero. 

Butane, C 4 Hi , is the first of the series capable of existing in 
two forms, isomers. The structural formulae of these two com- 
pounds are shown in the illustration of the term isomer on 
page 185. This compound, as well as the next higher homologue 
pentane, C5H12, are of importance only in their relation to some 
of their derivatives which will be subsequently studied. 



DOUBLE-BONDED HYDROCARBONS. 

If two carbon atoms are united by a double bond, as in 
H H 

^C = c' (C 2 H 4 ), chlorin may be added directly by the 
H H 

breaking of the double bond, forming ethylene chlorid, 

V_,2-H-4^l2' 

Note that the formula of ethylene does not conform to the 
general formula of the paraffins (C n H 2n+2 ), but is the first 
member of the new series of " unsaturated " hydrocarbons; 
the olefin or ethylene series with a general formula of C n H 2n - 

The hydrocarbons of this series take their names from corre- 
sponding members of the paraffin series, with "ene" as a dis- 
tinguishing termination — ethylene, C 2 H 4 , propylene, C 2 H 6 , 
butylene, C 5 Hi , etc. They are unimportant in dental or physio- 
logical chemistry. Some of the higher oxygenated compounds 
of this class are, however, of great importance, as olein, which 
is a constituent of vegetable and animal fats and oils. 



190 ORGANIC CHEMISTRY 

TRIPLE-BONDED HYDROCARBONS. 

A third series of the straight chain hydrocarbons is the 
acetylene series; these are triple bonded, and of course unsatu- 
rated, with a general formula of C n H 2 n-2. 

The only members of this series of special interest are, first, 
acetylene, H — C = C — H, (C2H2), made from calcium carbid 
and water. It is poisonous, combining directly with the haemo- 
globin of the blood, has a disagreeable odor, and is inflammable; 
second, allylene, C 3 H 4 , derivatives of which occur in onions, 
garlic, mustard-oil, etc. 

Laboratory Exercise LI. 
Experiments with Carbon and Hydrocarbons. 

Exp. 45. Carbon as a decolorizing agent. To 25 or 30 c.c* 
of a dilute solution of aniline color, contained in a small beaker, 
add a teaspoonful of bone charcoal. Heat to the boiling-point, 
rotate or stir thoroughly for a few minutes, and filter. 

Exp. 46. Absorption of metallic salts. To 25 c.c. of solu- 
tion of lead acetate of such strength that H 2 S water gives marked 
color but no precipitate, add a teaspoonful of bone charcoal and 
treat as in preceding experiment. Test the filtrate with H 2 S 
water and note whether lead has been removed. 

Exp. 47. Perform an experiment with a view to determin- 
ing whether bone charcoal will absorb H 2 S from H 2 S water. 

Exp. 48. Repeat either of the three immediately preceding 
experiments, using wood charcoal in place of bone charcoal. 
Does the wood charcoal work as well as the bone charcoal in 
the absorption of color or other substances? How does bone 
charcoal differ in composition from wood charcoal ? 

Exp. 49. 25 c.c. of crude petroleum in a boiling flask is 
connected with a long piece of tubing which serves as an air 
condenser. The flask is fitted to the thermometer and the 
contents heated slowly until at least three fractional products 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 191 

are obtained with boiling points differing by at least 15 . Note 
any other physical differences between the distillates thus ob- 
tained. 

Exp. 50. Charge an ignition- tube with dry " marsh-gas 
mixture," found on side shelf (consisting of NaC 2 H 3 2 , NaOH, 
and Ca0 2 H 2 ). Fit with a delivery-tube and collect two small 
bottles of the gas over water. 

NaC 2 H 3 2 + NaOH = CH 4 + Na 2 C0 3 . 

Test the inflammability of this gas. Notice the odor. 

Exp. 51. Mix carefully in a test-tube 2 c.c. of alcohol and 
8 c.c of strong sulphuric acid. Heat gently and notice odor of 
gas. Fit a bent glass tube to the test-tube and collect over 
water a test-tube full of the gas. To this apply a flame. Note 
the color of the burning gas. 

C 2 H 5 OH - H 2 = C 2 H 4 . 

Haloid Derivatives of the Paraffins. 

Methane furnishes three chlorin substitution products which 
are more or less in common use : first, the monochlor-methane, or 
methyl chlorid; second, the trichlor-methane CHC1 or chloroform, 
and third, the tetrachlorid of carbon CC1 4 . 

Methyl Chlorid, CH 3 C1, may be made from methyl alcohol, 
zinc chlorid, and hydrochloric acid. It is a colorless gas, con- 
densing to a liquid at 23 C. ; used as a spray in producing local 
anaesthesia (page 172) ; also as a constituent of anaesthetics, such 
as anesthol, somnoform, etc. 

Dichlor-methane, C.H 2 C1 2 , also known as methylene chlorid, 
has been used as a general anaesthetic usually mixed in more or 
less chloroform and alcohol. Its use in this way is open to 
criticism because of its poisonous action, affecting the heart. 

Chloroform, CHC1 3 , trichlorme thane, is a general anaesthetic 
prepared by distilling a mixture of chlorinated lime and acetone. 
Alcohol and water were formerly used in place of acetone (see 



192 ORGANIC CHEMISTRY 

Exp. 56, page 193). While it is not regarded as inflammable, 
its heated vapor can be made to burn with a greenish flame. 

Methyl Chloroform, CH3CCI3, formed by replacing the H 
atom of chloroform by a methyl group, CH 3 , has been used as 
an anaesthetic. 

Tetrachlorid of carbon is a colorless liquid used quite largely 
as a solvent. It also has anaesthetic properties, but like dichlor- 
methane, is dangerous because of its action on the heart. 

Methyl bromid, or monobrom-methane, is used to some ex- 
tent as a constituent of anaesthetics. 

Bromoform, CHBr 3 , tribrom-me thane, is prepared from 
bromin and a solution of alcoholic potash. Its properties are 
similar to those of chloroform, but it is more poisonous. 

Methyl Iodid, CH 3 I, is a heavy liquid, with pleasant 
odor, boiling-point 43 C; has been used somewhat as a 
vesicant. 

Iodoform, HC1 3 , tri-iodome thane, is a much-used and very 
valuable antiseptic. It is a light-yellow crystalline powder 
with characteristic persistent odor (Plate V, Fig. 1, page 222). 

Iodoform may be made by heating in a retort two parts of 
potassium carbonate, two of iodin, one of strong alcohol, and five 
of water, till the mixture is colorless. 

Iodoform is also produced from action of the above reagents 
with acetone in place of alcohol. This test is a very deli- 
cate one and advantage is taken of it in testing for acetone in 
saliva, which see. 

Ethyl Chlorid, C 2 H 5 C1, chlorethyl, may be made by dis- 
tillation of a mixture of alcohol and hydrochloric acid and 
purification of the distillate. It is extremely inflammable, boils 
at 12 C, and is used as a local anaesthetic in similar manner to 
methyl chlorid. Its higher boiling-point makes it the more 
convenient of the two preparations (see page 1^9). 

Ethyl Bromid, C 2 H 5 Br, prepared from alcohol, sulphuric 
acid, and potassium bromid. It is a heavy colorless liquid, 



THE HYDROCARBONS AND SUBSTITUTION PRODUCTS 193 

does not burn, and has been used to considerable extent as a 
general anaesthetic. 

Laboratory Exercise LII. 

Experiments with Hydrocarbons (continued) and their Halogen 

Derivatives. 

Exp. No. 52. Shake together, in separate test-tubes, small 
quantities of petroleum and sulphuric acid in one tube, and 
petroleum and nitric acid in the other. If no action results, mix 
contents of the two tubes and shake again. Explain any change 
or absence of change which may be apparent. 

Exp. 53. In a small generator (see model) place a few small 
pieces of calcium carbid (CaC 2 ), add strong alcohol through the 
funnel tube till the lower end of the tube is "sealed." Now 
add very slowly a little water till a brisk evolution of gas is 
obtained. Collect over water two or three test-tubes full of the 
gas. (Acetylene.) 

Test with a lighted splinter. Note odor of gas cautiously, 
as it is poisonous when inhaled in quantity. 

CaC 2 + 2 H 2 = Ca(OH) 2 + C 2 H 2 . 

Exp. 54. Conduct a little of the acetylene gas into an am- 
moniacal cuprous chlorid solution. What is the red precipitate ? 

Exp. 55. If the evolution of gas has not been interrupted 
the delivery-tube may be replaced by a short tube drawn out 
to a fine point and the gas ignited. Note color of flame. If 
it smokes badly, explain the reason for it. 

Exp. 56. Place in a test-tube a little bleaching-powder, 
cover with strong alcohol and heat the mixture to boiling. 
Notice carefully the odor of the vapor produced and compare 
with a little chloroform (CHCI3) from side shelf. 

4 C 2 H 5 OH + 8 Ca(C10) 2 = 2 CHC1 3 + 3 Ca(CH0 2 ) 2 

(Formate of Ca) 

+ 5 CaCl 2 + 8 H 2 0. 



194 



ORGANIC CHEMISTRY 



Exp. 57. Place in a test-tube about 1 gram of crystallized 
carbonate of sodium, about half as much iodin and 1 or 2 c.c. of 
alcohol. Now add 10 or 15 c.c. of H 2 and keep the mixture 
at moderate heat (not boiling) till the color of the iodin is dis- 
charged. Allow to cool; collect on a small niter-paper some of 
the yellow crystals which have been formed and examine under 
the microscope. What are the crystals? Explain their rela- 
tion to marsh-gas. 






CHAPTER XXII. 
ALCOHOLS. 

If we substitute for one of the hydrogen atoms of methane, 
a hydroxyl group (OH), we shall produce the first of a series of 
alcohols, several of which will claim our attention. 

The alcohols may be considered as hydroxids of alkyl * radi- 
cals, CH3OH being methyl alcohol; C 2 H 5 OH, being ethyl or 
ordinary alcohol; C3H7OH being propyl alcohol; and C 5 HnOH, 
amyl alcohol or fusel oil. 

The alcohols as a class may be prepared by the action of 
moist silver oxid on the corresponding halogen compounds; e.g., 

CH 3 Br + AgOH = CH 3 OH + AgBr. 

In many instances, the alkaline hydroxids will act in the 
same way. 

CH 3 Br + KOH = CH 3 OH + KBr. 

Alcohols treated with metallic sodium or potassium liberate 
hydrogen gas, forming compounds known as alcoholates; e.g., 

CH3OH + K = CH3OK + H; 
or C2H5OH + K = C2H5OK + H. 

While these compounds are, as just stated, called alcoholates, 
they may be distinguished, one from another, by using the name 
of the alkyl radical involved, and CH 3 OK will be potassium 
methylate, while C 2 H 5 OK will be potassium ethylate. 

Alcohols may contain more than one hydroxyl group, and, 

* Alkyl — a term used to denote any hydrocarbon radical as CH3-, C2H5-, C3H7-, 
etc. 

i95 



196 ORGANIC CHEMISTRY 

according to number of the OH groups, are termed mono-, di-, 
tri-a tonne, etc. Thus, ordinary alcohol, C 2 H 5 OH, is mono- 
atomic; glycerol, C 3 H 5 (OH) 3 is triatomic, while mannite 
C 6 H 8 (OH) 6 is a hexatomic alcohol. 

Alcohols may also be classified according to the relative 
position of the hydroxyl group. By this classification, we may 
have primary alcohols with OH replacing a hydrogen of the 
-CH 3 group; secondary alcohols with OH replacing the 
hydrogen of a -CH 2 group; and tertiary alcohol with OH re- 
placing the hydrogen of a -CH group. This may be illus- 
trated by the formula of an alcohol of each class. CH 3 -CH 2 
-CH 3 , being the hydrocarbon, a primary alcohol will have the 
formula CH 3 .CH 2 .CH 2 OH, and -CH 2 OH may be considered 
distinctive grouping of the primary alcohols. Again from the 
same hydrocarbon, if OH is substituted for an H of CH 2 
then the secondary alcohol will be CH3-CHOH-CH3 and 
-CHOH may be regarded as a distinctive group of this class. 

The tertiary alcohols, however, must be produced from com- 
pounds having at least four carbon atoms, as a CH group is 
only possible when there are sufficient carbon atoms to produce 
a forked chain; that is, in a compound with three carbon atoms, 
one must of necessity be placed between the other two, while 
with four carbon atoms, the carbons may be attached in a 
straight chain, such as C-C-C-C, or they may be arranged as 

y C 

a forked chain C-C x , and by supplying the hydrogen atoms 

necessary to satisfy the valence of each carbon, in this latter 
chain we find a CH group. OH introduced in place of the 
hydrogen of this group gives us the tertiary alcohol, 

/CH 3 
CH 3 -COH( ch . 

Notice that the forked chain gives us possible isomeric com- 
pounds. 



ALCOHOLS 197 

The hydroxyl derivatives (alcohols) of isopentane are well 
suited to illustrate the three (primary, secondary, and tertiary) 
characteristic alcohol groupings. 

CH 3X 

CH-CH2-CH3 is isopentane 
CH3' 

and by introducing the OH group (hydroxyl) into the CH 3 
group there is formed a primary amyl alcohol, 

CH 3X 

CH-CH 2 CH 2 OH, or isobutyl carbinol, 
CH 3 X 

and the primary alcohol grouping is -CH 2 OH. By introducing 
hydroxyl (OH) into the CH 2 group we should have -CHOH- 
as a characteristic combination in secondary alcohols, 

CH 3N 

CH; 



CH-CHOH-CH 3 , methylisopropyl carbinol; 



and lastly, by putting the OH in place of the H of the CH group 
of the hydrocarbon, we should have (CH 3 ) 2 = COH-CH 2 -CH 3 , 
a tertiary alcohol with the group = COH as its characteristic. 

Methyl Alcohol, CH 3 OH, (H-CH 2 OH),* wood spirit, carbi- 
nol, is a product of the destructive distillation of wood or can 
be made synthetically from methane. It is a colorless, inflam- 
mable liquid, with a gravity of 0.802 at 15 C, with solvent 
properties similar to ordinary alcohol, and boils at 66°. 

Ethyl Alcohol, C 2 H 5 OH, (CH 3 -CH 2 OH), methyl carbinol, 
grain alcohol, or ordinary alcohol is made by fermentation of 
solutions of various carbohydrates and purified by distillation. 
Carbon dioxid is evolved as follows : 

C 6 H 12 6 = 2 C 2 H 5 OH + 2 C0 2 . 

95% alcohol has a specific gravity 0.8164, boils at about 
78 C, dissolves many inorganic salts, vegetables, waxes, resins 

* Note that CH 2 OH is the "alcohol group" peculiar to this class of alcohols. 



198 ORGANIC CHEMISTRY 

(not gums), oils, etc., and is miscible with water, ether, or 
chloroform. 

Amyl Alcohol, C 5 HnOH, (C4H9-CH2OH), isobutyl carbinol, 
is a colorless, oily liquid with a specific gravity of 0.818. It 
boils at about 130 C, and burns with a bluish flame. 

Fusel-oil, or potato spirit, consists of amyl alcohol carrying 
traces of various other alcohols as impurities. 

Amyl alcohol is a valuable solvent and is largely used in the 
manufacture of artificial fruit flavors, banana essence, and the 
like. 

Oxidation of the Alcohols. 

Aldehyds. 
The first step in the oxidation of an alcohol consists not in 
the addition of oxygen but in the withdrawal of hydrogen; thus 
the oxidation of methyl alcohol produces formaldehyd (CH2O) 
and water. 

CH3OH + O = CH 2 + H 2 0. 

Aldehyds may be considered compounds containing an alkyl 

H H 

/ I 

radical and a distinctive group, -C ; thus CHO is formaldehyd, 

O 
CH 3 , is acetaldehyd, etc. (compare Alcohol, page 197). 
I 
CHO 

Formaldehyd coagulates albumen and hardens gelatin; when 
used as a preservative it renders the proteins tougher and less 
digestible. 

Formaldehyd polymerizes, producing the paraform or para- 
formaldehyd of trade, trioxymethylene, with a probable for- 
mula of (CH 2 0)3. It also forms one lower polymer (CH 2 0) 2 and 
at least one higher, formose, a substance allied to glucose. 

Acetaldehyd, aldehyd, CH3-CHO or C 2 H 4 0, the aldehyd 
from ethyl alcohol, may be made by addition of H 2 S0 4 to a 



ALCOHOLS 199 

mixture of alcohol and bichromate of potassium. It is a color- 
less, inflammable liquid with pungent etherial odor and boils 
at 22 C. 

Paraldehyd, (C 2 H 4 0) 3 a polymer of acetaldehyd, is a " color- 
less liquid with a strong pungent odor, soluble in 8.5 parts of 
water at 15 C, miscible in all proportions with alcohol, ether, 
and fixed or volatile oils. " (U. S. P.) It is a valuable hypnotic. 

Chloral, CCI3CHO, trichloraldehyd, is an oily liquid formed 
by action of dry CI gas on pure alcohol; soluble in ether and 
chloroform, boiling at from 94 C. to 98 C, and forming, with 
a molecule of H 2 chloral hydrate, CCI3CHO.H2O, a crystalline 
solid, and this is the " chloral" of the pharmacopoeia (see page 

167). 

Chloral hydrate is decomposed by sodium or potassium 
hydrate with liberation of chloroform (see Exp. 72, page 211): 
CCI3-CHO + KOH = CHCI3+ KCOOH (potassium formate). 

Upon warming a drop or two of aniline oil in an excess of 
alcoholic potash, chloral hydrate forms, first, chloroform, then 
phenylisocyanid, C 6 H 5 NC, the persistent disagreeable odor of 
which furnishes a delicate test for chloroform or chloral (see 
Exp. 73, page 211). By using CHC1 3 as the reagent in place of 
the aniline, the same reaction becomes a test for aniline or 
organic compounds, from which aniline may be produced by 
heating with alcoholic potash as acetanilid. Other aldehyds 
from hexatomic alcohols are dextrose (glucose) and galactose. 
They are represented by the formula CH 2 OH-(CHOH) 4 -CHO > 
and will be considered more fully in a subsequent lecture. 

Laboratory Exercise LIII. 

Alcohols and Aldehyds. 

Exp. 58. The detection of water in alcohol. Prepare a 
little anhydrous copper sulphate by heating a few crystals of 
CuS0 4 on a crucible cover until the water is driven off and a 



200 ORGANIC CHEMISTRY 

nearly white powder results. If this white powder, after boil- 
ing, is added to a half a test-tube full of alcohol, the absorption 
of water, if present, will result in reforming the crystallized salt 
and a consequent production of blue color. 

Exp. 59. Water may be separated from alcohol by saturat- 
ing with potassium carbonate. To demonstrate this, take a 
mixture of alcohol and water, containing 15 or 20 per cent of 
alcohol, and add solid potassium carbonate until the salt will 
no longer dissolve. Agitate and allow to stand. Two layers 
will form, one consisting of alcohol the other of the water solu- 
tion of K2CO3. 

Exp. 60. To about 75 c.c. of a 10% glucose solution add 
a little yeast and allow to stand for twenty-four hours at a 
temperature of about 37°C; then distil by means of gentle 
heat 10 or 15 c.c, and test distillate for alcohol by iodoform test, 
as given on page 194, Exp. 57. The production of CO2 may 
also be demonstrated if the gases evolved during the fermentation 
are passed into clear lime-water: 

C 6 H 12 6 = 2 C2H5OH + 2 C0 2 . 

Exp. 61. A test for methyl alcohol. This test is applicable 
only to slight traces of methyl alcohol and may be made with 
a 1 to 2 per cent solution or with the first cubic centimeter of 
distillate from the substance suspected of containing methyl 
alcohol. Place 2 or 3 c.c. of very dilute methyl alcohol in a 
test-tube, heat a spiral of copper wire to white heat in a Bunsen 
flame and plunge immediately into the solution to be tested. 
Cool the contents of the tube by immersion in freezing mixture 
or ice water, and repeat the treatment with the hot copper wire. 
Cool again, and a third time introduce the hot copper wire. 
The copper spiral can be made by winding copper wire around a 
lead pencil, and should be of such a length that it is not wholly 
covered by the liquid in the tube. 

This process serves to oxidize a portion of the alcohol to 



ALCOHOLS 20 1 

aldehyd. Now add to the solution which is being tested a few 
drops of a 1/2% water solution of resorcin and underlay the 
mixture with strong sulphuric acid. A violet ring will indicate 
the presence of methyl alcohol. The higher alcohols will give 
red or brown rings when similarly treated. 

Exp. 62. Mix about 1 c.c. of a very dilute solution of 
formaldehyd with four or five times its volume of milk in a test- 
tube. Carefully underlay the mixture with commercial sul- 
phuric acid of a specific gravity of 1.80. At the point of contact 
of the two layers of liquid a violet-colored ring indicates the 
presence of formaldehyd. It is necessary that the sulphuric 
acid should contain a trace of iron : this the commercial acid usu- 
ally does. It is also undesirable that the acid should be stronger 
than of 1.80 specific gravity; for, if it is, a reddish-brown ring 
may be formed, due to partial carbonization of the casein. 

Exp. 63. To about 5 c.c. of a strong aqueous solution of 
potassium dichromate add a little sulphuric acid, then a few 
cubic centimeters of alcohol, and notice the odor of acetaldehyd 
produced by oxidation of the alcohol. Note also the reduction 
of the dichromate to Cr 2 (S0 4 ) 3 , as follows: 

K 2 Cr 2 7 -f 4 H 2 S0 4 + 3 C 2 H 5 OH = 

K 2 S0 4 + Cr 2 (S0 4 ) 3 + 3 C 2 H 4 + 7 H 2 0. - 

Exp. 64. Test a dilute solution of both formic and acetic 
aldehyd by Tollen's test for aldehyd as follows: Into a clean 
test-tube which has been rinsed with NaOH solution, place 5 c.c. 
of Tollen's reagent, add 10 c.c. of solution to be tested, shake; 
the silver is reduced, forming a metallic mirror on the inner sur- 
face of the tube. 

To make Tollen's reagent, dissolve 3 grams of silver nitrate 
in 30 c.c. ammonia water and add 3 c.c. of solution of sodium 
hydroxid. 



202 ORGANIC CHEMISTRY 



Ketones. 

The oxidation of secondary alcohols (page 196) will not yield 
aldehyds, but a class of substances known as ketones: 

(CH 3 ) 2 -CH-CHOH-CH 3 + O = (CH 3 ) 2 -CH-C : O-CH3+ H 2 0, 

A secondary alcohol. Methyl isopropyl ketone. 

Methyl isopropyl carbinol. 

or CH3-CHOH-CH3 + O = CH3-CO-CH3 + H 2 0. 

Isopropyl alcohol. Dimethyl ketone. 

The converse of each of these reactions is possible, and, by 
reduction of a ketone with nascent H (sodium amalgam), the 
secondary alcohol will be formed: 

CH3-CO-CH3 + H = CH3-CHOH-CH3. 

Acetone. Isopropyl alcohol. 

Likewise primary alcohols may be produced by the reduc- 
tion of aldehyds: 

CH3-CHO + H 2 = CH 3 -CH 2 OH. 

Acetaldehyd. Ethyl alcohol. 

Note that the grouping peculiar to ketone is = CO or -CO-. 

Acetone, or dimethylketone, CH3-CO-CH3, a colorless liquid 
of peculiar odor, boils at 5 6° C. and is made commercially by 
the dry distillation of acetate of lime. 

It occurs in the blood and urine of patients suffering from 
advanced diabetes. According to von Noorden, the acetone 
found in the blood is formed by an intracellular process and in- 
dicates an acid auto-intoxication and an insufficient utilization 
of carbohydrates. In the experience of the author, acetone may 
sometimes be found in the saliva when it cannot be found in 
the urine (for test, see Acetone under Saliva and Urine). 

Another ketone of interest is laevulose, fruit-sugar, CH 2 OH- 
CHOH.CHOH.CHOH.CO.CH 2 OH, which, with glucose, will be 
studied later. 



ALCOHOLS 203 

While the oxidation of a primary alcohol will produce an 
aldehyd and the oxidation of a secondary alcohol will produce 
a ketone, the tertiary alcohol, by action of an oxidizing agent, 
is split into two new carbon compounds, that is, the chain is 
broken and simpler ketones and acids are formed. 



CHAPTER XXIII. 
ETHERS. 

Ethers may be regarded as oxids of the hydrocarbon radi- 



C2H5 



cals, as 0, or as anhydrids of the monatomic alcohols, 

C2H5 
H 2 having been removed from two molecules of the alcohol: 

2 C 2 H 5 OH-H 2 = (C 2 H 5 ) 2 0. 

Ethers may be simple, mixed, or compound. The simple 
ether is illustrated above by the formula for ordinary or ethyl 
ether, where two radicals of the same kind are united by an 
atom of oxygen. 

In a mixed ether, these radicals will be of different kinds; 
as, for example, CH 3 -0-C 2 H 5 , methyl-ethyl ether. 

The compound ethers are compounds of alcohol radicals 
with acid radicals, that is, the salts of alcohol radicals. The 
acid may be either organic or inorganic; thus, we have nitric 
ether, ethyl nitrate, C 2 H 5 N03, and we have acetic ether, ethyl 
acetate, C 2 H 5 C 2 H 3 2 . The compound ethers are often called 
esters and form a large and important class of organic com- 
pounds. 

A general method for the preparation of simple and mixed 
ethers is that of distillation of the corresponding alcohols with 
sulphuric acid, as illustrated by experiment No. 69, page 210. 
They may also be produced by the action of silver oxid on the 
corresponding alkyl iodids: 

2 C 2 H 5 I + Ag 2 = (C 2 H 5 ) 2 + 2 Agl, 

also, by treating the sodium alcoholate with an alkyl iodid, 

204 



ETHERS 205 

k C 2 H 5 ONa + C 2 H 5 I = (C 2 H 5 ) 2 + Nal 



CH 3X 
or CHaONa + C 2 H 5 I = + Nal. 

' 2 H 5 



C2H5 



Methyl Ether. — Methyl oxid, (CH 3 ) 2 0, also known as formic 
ether, is isomeric with ordinary alcohol, and may be made in 
a manner similar to that used in the production of ethyl ether 
(q. v.). At ordinary temperature it is a gas, but liquefies at 
— 20 C. (Bernthsen). It has been used as a general anaesthetic, 
and the anaesthesia is said to be profound and quickly pro- 
duced (U. S. D. from A. J. P., Sept., 1870). 

Methyl-ethyl Ether. — This name, besides indicating a 
definite compound as referred to in the preceding paragraph, 
has been applied to a mixture of methyl ether and ethyl ether, 
used for purposes of general anaesthesia. 

Methylene Ether. — A name applied to a mixture of methyl- 
ene dichlorid and ethyl ether, used as an anaesthetic, but it has 
been found unsafe (U. S. D.). 

Ethyl Ether. — Ethyl oxid, (C 2 H 5 ) 2 0, consisting of 96% by 
weight of the " aether" of the pharmacopoeia (the other 4% be- 
ing alcohol and a little water). Ether is a general anaesthetic, 
widely used. It is made by the action of sulphuric acid on 
ethyl alcohol, and from this fact has been known as sulphuric 
•ether, but this name is, of course, incorrectly used, sulphuric 
ether being properly an ethyl sulphate (C 2 H 5 ) 2 S0 4 . 

In the preparation of ether, sulphuric acid may be mixed with 
rather more than its own bulk of alcohol, the mixture heated to 
a temperature of from 130 to 13 8° C. in a suitable retort or 
still, the distillate (ether) being collected in a cold receiver. 

The reaction takes place in two steps, as follows : One mole- 
cule of acid and one of alcohol react to form ethyl sulphuric 
acid (ethyl acid sulphate) and H 2 0, H 2 S0 4 + C 2 H 5 OH = 
C 2 H 5 HS0 4 + H 2 0. Then the ethyl sulphuric acid reacts with 



206 ORGANIC CHEMISTRY 

a second molecule of alcohol to form ether and sulphuric acid, 
C0H5HSO4 + C 2 H 5 OH = (C 2 H 5 ) 2 + H 2 S0 4 . Thus the sul- 
phuric acid, from two molecules of alcohol, has produced one 
molecule of ether and is in condition to repeat the process, hav- 
ing suffered itself only to the extent of adulteration with one 
molecule of water. In accordance with this theoretic forma- 
tion of ether by simple dehydration of alcohol by H 2 S0 4 , pro- 
vision is made for a continuous process, by the introduction of a 
constant supply of fresh alcohol into the retort during the dis- 
tillation, and so regulated that the total bulk of liquid is neither 
increased nor diminished. The product is then purified, and 
freed from water and traces of acid by redistillation over a mix- 
ture of lime and calcium chlorid. 

Ether, according to the U. S. P. requirements, is " a trans- 
parent, colorless, mobile liquid with characteristic odor and 
a burning and sweetish taste"; specific gravity of 0.725 to 0.728 
at 1 5 C. and boiling at about 37 C. It is readily inflam- 
mable, and this fact, together with its easy volatility, makes 
it necessary to use considerable care when handling it. 
Absolute ether boils between 34° and 35 C. 

The action of sulphuric acid upon alcohol needs careful 
regulation ; because there may be produced three other products 
in addition to the ethyl oxid already considered. These are, 
first, ethyl sulphuric acid, C 2 H 5 HS0 4 ; second, ethyl sulphate 
(C 2 H 5 ) 2 S0 4 , these being respectively the acid and neutral ethyl 
esters of H 2 S0 4 ; third, the hydrocarbon ethylene, C 2 H 4 . 
This latter compound is the first of the ethylene series of 
hydrocarbons with the general formula C n H 2n , and contain- 

ing "double-bonded" carbon atoms, C = C or CH 2 = 

CH.CH 3 . These are unsaturated hydrocarbons (see page 189). 
Ethylene is produced by the action of an excess of concentrated 
H 2 S0 4 , which abstracts H 2 from each molecule of alcohol 



ETHERS 207 

(C2H5OH— H 2 = C 2 H 4 ), whereas in the preparation of ether the 
more dilute acid abstracts H 2 from two C 2 H 5 OH. 

Compound Ethers or Esters. 

One of the most important of this class of compounds, from 
a dental standpoint, is the benzoyl-ecgonine methyl ester or 

(C 5 H 7 
cocain, CH 3 N < While of considera- 

( CH.C 7 H 5 2 .CH 2 .C0 2 CH 3 
ble interest, the elucidation of the exact chemical relationship of 
this compound to tropa-cocain, etc., is beyond the scope of this 
work. 

Another methyl ester of much simpler chemical composition 
is methyl salicylate, CH4-CH-COOCH3. 

Salicylic acid is CH 4 -OH-COOH (oxybenzoic acid), and 
its methyl ester constitutes the methyl salicylate of the U. S. P. 
It is identical with the volatile oil of betula and with 90% 
of the oil of gaultheria (wintergreen) . This latter oil is much 
used as a flavor in dental preparations, tooth-washes, powders, 
etc. 

Ethyl Acetate, CH 3 -COO.C 2 H 5 , is formed by heating ethyl 
alcohol, sulphuric acid, and acetate of sodium. This reaction 
constitutes a qualitative test for acetic acid or acetates, the 
odor of the ester being sufficiently characteristic to furnish 
a delicate test (page 94). 

The acetic ether of the U. S. P. is u a liquid composed of 
about 98.5% of ethyl acetate and 1.5% alcohol." 

Ethyl Butyrate, CH 3 -CH2-CH 2 -COOC 2 H 5 . This ester dis- 
solved in 10 parts of alcohol forms pineapple essence. It 
may be made in a manner similar to the preparation of ethyl 
acetate, i.e., by heating together alcohol, butyric acid, and 
concentrated sulphuric acid. The production of the ester is 
likewise used as a qualitative test for the presence of the acid, 
and employed in the examination of gastric contents as follows: 



208 ORGANIC CHEMISTRY 

" Heat 10 ex. of contents with 5 ex. of strong sulphuric acid 
and 4 ex of 95% alcohol: odor of pineapple indicates butyric 
acid." (Hewes.) 

Ethyl Nitrite, C2H 5 N0 2j may be made by heating sodium 
nitrite with concentrated sulphuric acid and alcohol, also by 
the reduction of nitric acid by copper in presence of alcohol 
and sulphuric acid. The ethyl nitrite is distilled, and must 
be collected in a receiver surrounded by a freezing mixture of 
ice and salt. Pure ethyl nitrite boils at 18 C, and has a gravity 
of 0.900. An alcoholic solution constitutes sweet spirits of 
nitre, the spiritus aetheris nitrosi of the U. S. P. 

This preparation should, according to Dr. E. R. Squibb, 
contain 4.5% ethyl nitrite. 

Amyl Acetate and Amyl Butyrate may be obtained by heat- 
ing the respective acids with amyl alcohol (C5H11OH) and strong 
sulphuric acid. These esters may also be used in detecting the 
presence of the acid, amyl alcohol being used in place of ordinary 
alcohol. Amyl acetate gives the odor of pears 2 amyl butyrate 
that of bananas. 

Amyl nitrite, C 5 HnN0 2 , is a compound used in medicine to a 
considerable extent, usually administered by inhalation. The 
U. S. P. preparation contains about 80% of amyl nitrite. It is 
very soluble and inflammable. 

The Fats are esters of glyceryl, C 3 H 5 , also called tritenyl, 
propenyl, etc. This radical forms with hydroxyl (OH) the pro- 
penyl alcohol, C 3 H 5 (OH) 3 , which is ordinary glycerin or glycerol. 

Glyceryl butyrate or butyrin, CH3-(CH 2 )2-COOC 3 H5, con- 
stitutes (together with smaller quantities of the glyceryl esters 
of capric, caproic, and caprylic acids) about 7% of butterfat. 
These esters are readily saponified by treatment with alcoholic 
potash; then, by decomposition of the potassium salts with 
H 2 S0 4 , the acids, being volatile, may be separated by distillation. 
The amount of volatile fat acids thus obtained is a valuable test 
for the genuineness of the butter. 



ETHERS 209 

Glyceryl Palmitate, C 3 H 5 (Ci 6 H3i0 2 )3, tripalmitin ; glyceryl 
stearate, C 3 H 5 (Ci 8 H350 2 )3, tristearin, and glyceryl oleate, 
C 3 H 5 (Ci8H3302)3, triolein; these in varying proportions make up 
the greater part of animal and vegetable fats and oils. 

The prefix "tri" is used because the "mono" and "di" 
compounds, as monopalmitin, C3H 5 (OH) 2 -Ci 6 H3i0 2 , etc., are 
possible and may be prepared by synthesis. Triolein is liquid 
at ordinary temperature, solidifies at -6° C, is a "double- 
bonded" compound, hence forms addition-products with the 
halogens as stearin and palmitin cannot do, they being "satu- 
rated hydrocarbons. " 

The amount of chlorin or bromin which a fat or oil can thus 
absorb is an index of the proportion of unsaturated fatty acids 
contained in it, and hence becomes a valuable method of 
identification. Olive-oil and lard-oil contain large amounts of 
olein. 

Tripalmitin melts at 66° C, is usually obtained from palm- 
oil. Tristearin melts at 72 C, occurs with palmitin and olein 
in beef-fat, mutton- tallow, etc., the consistence of the fat being 
dependent upon the proportions of the constituent esters. 

The fats, stearin for example, may be split into glycerol and 
fatty acid by steam under pressure as follows : 

C3H 5 (C 18 H 3 50 2 ) 3 + 3 H 2 = C 3 H 5 (OH) 3 + 3 HC 18 H 35 2 . 

A partial result of this sort is brought about by the fat- 
splitting enzyme (lipase) of the pancreatic juice (see Steapsin). 
Saponification of the fats by caustic alkali takes place as 
follows : 

C 3 H 5 (C 18 H 35 2 ) 3 + 3 KOH = C 3 H 5 (OH) 3 + 3 KC 18 H 35 2 . 

The potassium salts of the fatty acids constitute the soft 
soaps, while the sodium salts are in general the hard soaps. 
The "salting-out" process in soap manufacture brings about 
a double decomposition resulting in the production of ordinary 
soap. 



2IO ORGANIC CHEMISTRY 

Laboratory Exercise LIV. 
Experiments with Acetone and Ethers. 

Exp. 65. Preparation of Acetone: Heat a few grams of 
dried calcium acetate in an ignition tube, collect the distillate, 
which consists of an impure acetone. If this is mixed with a 
little water and filtered, part of the impurities may be removed, 
and the filtrate tested for acetone by the following experiment. 

Exp. 66. Dilute the nitrate from the last experiment with 
distilled water; add a crystal of potassium nitroprussid. After 
.the crystal is dissolved, add a few drops of acetic acid, and then 
an excess of ammonia water. A violet or purple color indicates 
the presence of acetone. Using a dilute solution of acetone in 
place of the alcohol in experiment 57, on page 194, produce iodo- 
form crystals by similar reaction with iodin and sodium or po- 
tassium carbonate. 

Exp. 67. Acetone may be dissolved or mixed with water in 
all proportions; but, upon saturating the water with KOH, 
the acetone will form a separate layer which may be drawn off as 
in the separation of alcohol in experiment 59, page 200. 

Exp. 68. To a dilute aqueous solution of acetone add 
potassium permanganate slowly until the mixture is perma- 
nently colored pink; filter, add dilute sulphuric acid and distil 
until 1 or 2 c.c. of distillate are obtained. This may be tested 
for acetic acid by litmus paper or ferric chlorid. 

Exp. 69. Into a large test-tube put a little alcohol and about 
half its volume of strong H 2 S0 4 . Warm gently and notice the 
odor. 

Ether is formed by two reactions. First, C 2 H 5 OH -f- H 2 S0 4 
= C2H5HSO4 + H 2 0. Then the ethyl-hydrogen sulphate 
(C 2 H 5 HS0 4 ) is acted upon by a second molecule of H 2 S0 4 , as 
follows: C 2 H 5 HS0 4 + C 2 H 5 OH = (C 2 H 5 ) 2 + H 2 S0 4 . 

Exp. 70. The production of compound ethers may be dem- 
onstrated by the test for acetic acid forming ethyl acetate, 



ETHERS 2 1 1 

page 94, or by the following experiment used to detect butyric 
acid in gastric contents: 

Exp. 71. Mix in a test-tube 5 ex. of a dilute (1/2%) solu- 
tion of butyric acid with an equal volume of strong H 2 S0 4 and 
as much strong alcohol. Heat gently and note the odor of 
ethylbutyrate (pineapples). 

Exp. 72. To about 5 c.c. of an aqueous solution of chloral 
hydrate add a few cubic centimeters of strong NaOH solution 
and boil. Note odor of chloroform. 

Exp. 73. Isobenzonitril test for chloral or chloroform: 
Place a few drops of a dilute chloral hydrate solution (or a 
small drop of chloroform) in a test-tube, add 5 ex. of an alco- 
holic solution of alkali hydrate * (NaOH or KOH) and one drop 
only of fresh aniline oil. Heat till the mixture just begins to 
boil and note the odor of the nitril. 

* If alcoholic potash or soda is not at hand, the test may be performed with 
5 c.c. of alcohol and 1 or 2 c.c. of a 40% aqueous solution of NaOH. 



CHAPTER XXIV. 

ORGANIC ACIDS. 

If the oxidation of an alcohol is carried beyond the formation 
of aldehyd or ketone, i.e., if the aldehyd or ketone be oxidized, 
an organic acid results. The first atom of oxygen involved 
in this process does not become a constituent part of the new 
molecule, but simply withdraws hydrogen from the old (the 
alcohol), as shown in the formation of aldehyds on page 198. 
The second atom of oxygen, however, attaches itself to the 
molecule and does become a part of the new substance (the acid) : 

CH3 CH3 CH3 CH3 

I +0=| + H 2 I +0=| 
CH 2 OH CHO CHO COOH 

Alcohol. Aldehyd. Aldehyd. Acid. 

The group -COOH is known as carboxyl and is the char- 
acteristic grouping of the acids. The H of the carboxyl differs 
from the other atoms of H in the molecule in that it is united 
to oxygen rather than to carbon, and constitutes the basic or 
replaceable H of the acid; hence acetic acid is monobasic, and 
the only possible salt, of potassium, for instance, is CH3-COOK. 

The basicity of the acid depends on the number of carboxyl 
groups it contains. 

Among the monobasic acids of the fatty or paraffin series 
which we will study are the following: 

Representative Fatty Acids. 

H.COOH = formic acid or hydrogen formate; 
CH3.COOH = acetic acid or hydrogen acetate; 
C2H5.COOH = propionic acid or hydrogen propionate; 



ORGANIC ACIDS 213 

C3H7COOH = butyric acid or hydrogen butyrate; 

C4H9COOH = valeric acid or hydrogen valerate; 
C15H31COOH = palmitic acid or hydrogen palmitate; 
C17H35COOH = Stearic acid or hydrogen stearate. 

The acids of these series are represented by the general 
formula C n H 2n 2 . They are all monobasic; i.e., they contain 
only one atom of replaceable hydrogen. 

Formic Acid, (H.COOH), originally distilled from the bodies 
of ants (formica, from which the name is derived), is a colorless, 
easily volatile liquid. It may be prepared in the laboratory 
by heating oxalic acid with glycerol, when the oxalic acid breaks 
up into formic acid and CO2, 

C 2 H 2 4 = C0 2 + HCOOH. 

Carbon monoxid, passed over hot KOH, results in the forma- 
tion of potassium formate, 

CO + KOH = HCOOK. 

Also by treatment of ammonium carbonate with nascent hydro- 
gen (sodium amalgam) , 

C0 3 (NH 4 ) 2 + 2 H = HCOO(NH 4 ) + H 2 + NH 3 ), 
and 

HCOO(NH 4 ) + NaOH = HCOONa + NH 3 + H 2 0. 

Formic acid, according to the above reaction, is apparently 
carbonic acid less one atom of oxygen, and the fact that formic 
acid acts easily as a reducing agent, taking away oxygen from 
other bodies and becoming H 2 C03, is further proof of this 
relationship. 

Acetic Acid, CH3COOH, is obtained commercially by the 
oxidation of ethyl alcohol. It is the acid of vinegar, which, 
according to Massachusetts law, should contain 4.5% of acid. 
Glacial acetic acid is a commercial name of the acid contain- 
ing 1% or less of water: it is a colorless solid at a temperature 
below 1 5 C. The U. S. P. acetic acid contains only 36% (by 
weight) of the pure acid. 



214 ORGANIC CHEMISTRY 

Either one, two, or all three of the hydrogen atoms of the 
CH 3 group may be replaced by chlorin, forming respectively 
the mono-, di-, and tri-chloracetic acids, the trichloracetic acid 
being used to a considerable extent in dentistry (page 1 76) . 

Acetic acid, by the abstraction of water, forms an anhydrid, 
C4H6O3 : 

2 HC2H3O2 = (C 2 H 3 0) 2 + H 2 0. 

This substance is of considerable inportance in organic reac- 
tions. It is a colorless liquid with a boiling-point of 138 C, 
and, with the halogens, forms compounds such as acetyl chlorid, 
C2H3OCI, the radical C2H3O being known as the acetyl radical. 

Propionic acid, CH 3 .CH 2 .COOH, is a colorless liquid, 
boiling at 140 C. According to Witthaus, it is best prepared 
by heating ethyl cyanid with caustic potash until the odor of the 
ester has disappeared: 

C 2 H 5 CN + KOH + H 2 = C 2 H 5 COOK + NH 3 . 

Then, by treatment with H 2 S0 4 , the propionic acid is liberated, 
and may be separated by distillation. 

Butyric Acid, C3H7COOH, occurs as a product of fermenta- 
tion of butter, or other animal fat containing butyrin; also 
from the decomposition of lactic acid, two molecules of lactic 
acid furnishing one of butyric acid, 2 C0 2 and 2 H 2 . It is an 
occasional constituent of the gastric contents, and may be 
detected by formation of the ethyl ester (page 207). The pure 
acid is a heavy, colorless liquid with characteristic odor, soluble 
in H 2 in any proportion. See page 208 for the glyceryl ester 
of butyric acid (butyrin); also for stearic and palmitic acids. 

Valeric Acid, C4H9COOH, may be made by the oxidation of 
amyl alcohol (C5H11OH). It is an oily liquid boiling at 174 C. 
It occurs as a constituent of valerian, and in consequence has 
been called valeric acid. Its salts are used in medicine as seda- 
tives. 



ORGANIC ACIDS 215 

The valeriate of amyl has an odor resembling that of apples, 
and is used in alcoholic solutions as apple essence. 

Palmitic Acid, C15H31COOH, a solid "fat acid," occurs as a 
glyceryl ester in butter (to a very slight extent), in olive oil, 
palm oil, and bayberry wax. Combined with certain alcohols it 
occurs in white and yellow wax; also in spermaceti. 

Palmitin, C3H 5 (Ci 6 H 3 i02)3, occurs in all animal fat and in 
large quantities in human fat. 

Stearic Acid, C 18 H 3 5COOH[CH 3 -(CH 2 ) 16 -COOH], as glyceryl 
stearate or stearin occurs in vegetable and animal fats, particu- 
larly in tallow. Stearic acid is only slightly soluble in alcohol 
or in ether. Its melting-point is 69. 3 C. 

Laboratory Exercise LV. 
Experiments with organic acids. (C n H 2n 02). 

Exp. 74 and 75. Experiments 70 and 71 may be used as il- 
lustrating the laboratory test for acetic and butyric acids. In 
addition a test for lactic acid may be made with the ferric chlorid 
test, which is also applicable to gastric contents. Exp. 91, 
page 225. 

Exp. 76. Introduce into a small flask (250 c.c. capacity) 
about 30 c.c. of anhydrous glycerin and an equal weight of 
oxalic acid crystals. Boil for several minutes; C0 2 is given 
off and a compound formed between the acid and glycerin; 
then, upon addition of more acid and continued heating, formic 
acid may be distilled. Collect about 10 c.c. of distillate; test 
reaction with litmus-paper. Make silver-mirror test, described 
on page 201, Exp. 64. The silver solution will be reduced, but 
difficulty will be experienced in obtaining the mirror. 

Exp. 77. To 5 c.c. of formic acid solution add 2 or 3 c.c. of 
dilute H 2 S0 4 (1-5) and a little potassium permanganate solu- 
tion; heat the mixture and conduct the gas evolved into a 
tube containing lime water. 

Exp. 78. From a mixture of formic acid, alcohol, and sul- 



2l6 ORGANIC CHEMISTRY 

phuric acid, ethyl formate may be evolved in a manner similar 
to that in the production of ethyl acetate (page 95). Compare 
the odors of these two ethers. 

Exp. 79. To a dilute solution of ferric chlorid add a little 
acetic acid; divide the solution into two parts; to one add mer- 
curic chlorid and to the other HO, and note results. 

Exp. 80. Repeat Exp. 79, using diacetic acid in place of 
acetic. 

Exp. 81. Repeat Exp. 79 using meconic acid* in place of 
acetic. 

Compare results of these three experiments and save record 
for future use in the study of saliva. 

Exp. 82. In a small flask saponify a little butter by heating 
with alcoholic potash over a steam bath till mixture is dry. 
Dissolve in water, add dilute H 2 S0 4 , and distil off a portion of 
the butyric acid. Record whatever can be learned from this 
experiment regarding the physical properties of the butyric 
acid. 

Exp. 83. Take about 5 c.c. each of alcoholic solution of 
stearic and oleic acids and treat separately with about 1 c.c. of 
1% iodin solution (alcoholic) ; allow to stand for some time, and 
explain fully the difference in action exhibited by the two fatty 
acids. 

Acrylic Acid Series. 

Acrylic acid, CH 2 :CH.COOH, is a type of the double- 
bonded acids. It is a liquid with boiling-point at 140 C. Nas- 
cent hydrogen breaks the double bond, forming propionic acid, 
CH3.CH2.COOH. HI will also break the double bond by 
direct union of its constituents, forming CH 2 I-CH 2 -COOH, 
(/3-iodo propionic acid). 

Acrylic aldehyd, or acrolein, is a colorless liquid boiling at 
5 2 C. Its vapor has an irritating, pungent odor, sufficiently 

* Laudanum diluted with water till color is light brown may be used. 



ORGANIC ACIDS 217 

characteristic to be used as a qualitative test for glycerol, from 
which it is obtained by heating with KHS0 4 . 

The only other acid of particular importance in this series is 
oleic acid, C17H33COOH. It is an important constituent of oils, 
both animal and vegetable, and consists, to a great extent, of 
such substances as lard oil, cotton seed oil, etc. 

Dibasic Acids. 

COOH COOH COOH 

I I I 

COOH CH 2 CH 2 

I I 

COOH CH 2 



Oxalic acid. 



Malonic acid. 



I 

COOH 

Succinic acid. 



Dibasic acids contain two carboxyl groups. These are refer- 
able to, and in many cases may be formed from, the diatomic 

CH 2 OH 
alcohols. Thus glycol, I , upon oxidation yields gly collie 

CH 2 OH 
CH 2 OH COOH 

acid, I , and oxalic acid, I 

COOH COOH 

/OH 
Carbonic acid, O = C , is dibasic in that it contains two 

x OH 
atoms of replaceable hydrogen, though not two carboxyl groups. 
It is claimed that a molecule of this sort cannot exist because 
a single carbon atom cannot hold more than one hydroxyl group 
in combination. This acid has never been isolated, all attempts 
to separate it in the pure form resulting in the formation of 
carbonic acid gas and water. Its compounds (carbonates) are 
very common and very important, both in organic and inorganic 
chemistry. Organic salts of carbonic acid may be made by 
treating silver carbonate with alkyl iodid. 



2l8 ORGANIC CHEMISTRY 

y OAg /OC 2 H 5 

CO + 2 C 2 H 5 I = CO +2 Agl. 

X OAg X OC 2 H 5 

Oxalic Acid, which may be considered as a type of the di- 
basic acids, occurs as small, colorless crystals (four- or six-sided 
prisms), containing two molecules of water of crystallization 
(H0C2O4.2 H 2 0); it is but slightly efflorescent, and, if carefully 
crystallized, is suitable for the preparation of standard acid 
solution. Salts of oxalic acid occur in many plants; the acid 
potassium oxalate, "salt of sorrel," is found in common red 
sorrel (Rumex acetora) and in wood sorrel (Oxalis acetocella). 
Oxalic acid in various combinations, often with lime, is widely 
distributed in articles of vegetable diet, particularly tomatoes, 
rhubarb, spinach, and asparagus; grapes, apples, and cabbages 
also carry oxalates, but in smaller amounts. 

The source of oxalates in the system is twofold, — the in- 
gested oxalates and those produced by oxidation, incident to 
metabolism, the exact nature of which has not been clearly 
demonstrated (see Calcium and Sodium Oxalates, under Urine 
and Saliva). 

Oxalic acid was previously made commercially by the action 
of strong nitric acid on starch or sugar; it is now prepared by 
heating cellulose (in form of sawdust) with a mixture of KOH 
and NaOH, precipitating the acid as CaC 2 4 , and decomposing 
the salt by H 2 S0 4 . The acid is then purified by repeated 
crystallization. 

Malonic Acid, COOH-CH 2 -COOH, is an oxidation product 
of malic acid (from apples), and is comparatively unimportant. 

Succinic Acid, COOH(CH 2 )2-COOH, occurs in amber, from 
which it takes its name (Amber-Succinum) . It has been de- 
tected in the urine after asparagus and some fruits have been 
eaten. It occurs as colorless crystals, soluble in water, and only 
slightly soluble in ether. Succinic acid may be obtained by the 
saponification of ethylene cyanid, C 2 H 4 (CN) 2 , and is a dibasic 



ORGANIC ACIDS 219 

acid containing four carbon atoms. It is a constituent of some 
transudates and cyst fluids. It occurs in the spleen and thyroid 
gland, and has been found in sweat and in the urine (Ham- 
marsten) . 

Pyro-tartaric Acid, formed by the distillation of ordinary tar- 
taric acid, is one of four isomers of formula C 5 H 8 04, and is of 
interest only in its relation to some of the amino acids which 
result from protein digestion. Formula for pyro-tartaric acid 
is CH 3 -CHCOOH-CH 2 -COOH. 

Oxyacids. 

Hydroxy acids, or alcohol acids, contain hydroxyl in place 
of one or more hydrogen atoms of the fatty acids. Thus we 
may consider 

Carbonic acid as hydroxyformic acid, HO-COOH; 

CH 2 OH 

Glycolic acid as hydroxyacetic acid, I ; 

COOH 

C 2 H 4 OH 

Lactic acid as hydroxypropionic acid, I ; 

COOH 

Malic acid (from apples) as hydroxy- ^HOH-COOH 
succinic acid, CH 2 -COOH 

Tartaric acid is dihydroxy succinic CHOH-COOH 
acid ' CHOH-COOH 

Citric Acid, from lemons, limes, etc., is in a class by itself. 
It is a tribasic acid (has three carboxyl groups and one hydroxyl) ; 
the formula is C 3 H 4 OH-(COOH) 3 . 

Glycollic Acid occurs in nature in unripe grapes, and possibly 
as antecedent to oxalates in the system (Dakin, Journal of Biol. 
Chem., 3.57). Glycollic acid is formed from glycol by oxidation, 
and from glycocoll, by action of nitrous acid. 



220 ORGANIC CHEMISTRY 

Nitric acid will oxidize glycollic acid to oxalic acid. 

Lactic Acid. — Oxypropionic acid, or i * -ethylidene lactic 
acid, CH3-CHOH-COOH, is ordinary lactic acid produced by 
fermentation of milk-sugar, etc. It occurs in the gastric juice 
and in contents of the intestine, " particularly during a diet 
rich in carbohydrates," possibly in muscle and brain tissue 
(Foster). It is not volatilized at temperature below 160 C. 

Sarcolactic or paralactic acid, df-ethylidene lactic acid, 
occurs in meat extract. The presence of this acid causes the 
acid reaction of dead muscle, possibly of contracted muscle. 
It occurs in the blood and at times in the urine, and it is probable 
that it is this modification that may be found as lactates and 
acid lactates in the saliva and urine, the crystalline forms of 
which have been identified by Dr. E. C. Kirk of Philadelphia, 
by the use of the micropolariscopic method of Dr. Joseph P. 
Michaels of Paris. This statement as yet lacks confirmatory 
demonstration. 

Both of these acids form characteristic crystalline salts of 
zinc and of calcium. In cold water the zinc sarcolactate is 
more soluble than zinc lactate; on the other hand, the calcium 
sarcolactate is rather less soluble than calcium lactate. 

p-Oxybutyric Acid, CH 3 -CHOH-CH 2 -COOH. If there is 
introduced into butyric acid, CH3-CH2-CH2-COOH, an OH 
group, an oxy butyric results. If this alcohol group (OH) 
occupies the secondary or position (i.e., attached to the carbon 
atom twice removed from the carboxyl), the acid is the /3-oxy- 
butyric as above. 

By oxidation of the compound, the alcohol group is broken 
up and H withdrawn to form water, leaving a keto acid, 
CH 3 -CO-CH 2 -COOH, known as diacetic acid. This in turn 
may give off carbon dioxid and become dimethyl ketone, or 
acetone, CH3-CO-CH3. These three substances, /3-oxybutyric 
acid, diacetic acid, and acetone, are classed in von Noorden's 

* Optically inactive. t Dextrorotary. 



ORGANIC ACIDS 221 

" Autointoxication," and in the works of other recent writers, 
as "the acetone bodies," and by this convenient term we may 
refer to them collectively. They occur in diabetic urine and, 
according to von Noorden, in other cases of perverted oxidation 
(not insufficient oxidation). 

Tartaric Acid is a dihydroxysuccinic acid, COOH-(CHOH) 2 - 
COOH, obtained from grape-juice. The double tartrate of 
sodium and potassium (Rochelle salt), KNaC 4 H 4 6 , is much 
used in medicine. 

Tartaric acid combines with potassium and antimony to 
form tartar emetic, (KSbOC 4 H 4 6 ) 2 H 2 0. 

The "scale salts of iron" "ferri et ammonii tartras" and 
"ferri et potassii tartras," are prepared by dissolving freshly 
precipitated ferric hydroxid in the acid tartrate of ammonia or 
potash, and, after evaporation to thick syrup, solidifying in 
thin layers on glass plates. 

Potassium Bitartrate, or acid tartrate, KHC 4 H 4 6 , is cream 
of tartar, and one of the few salts of potassium, only sparingly 
soluble in water. Its commercial source is the wine-vat. 

Monobasic Amino Acids. 

Amino acids, formerly called amido acids, are characterized 
by an NH 2 group in place of H— ; for example, acetic acid is 

CH 3 CH 2 NH 2 

I . Amino acetic acid is I . These acids are of par- 

COOH COOH 

ticular interest because of their close relationship to protein, 
many of them being among the cleavage products of protein 
hydrolysis. 

. That many of the amino acids are formed as intermediate 
steps in the reduction of the complex protein molecules to urea 
is certain. 

A faulty metabolism, which stops short of normal oxidations, 



222 ORGANIC CHEMISTRY 

results in throwing these amino acids off in the urine or faeces 
and their presence indicates abnormal conditions of one sort 
or another. 

NH 2 
Amino formic or carbamic acid, I , is a hypothetical 

COOH 
acid which would consist simply of an amino group, NH 2 , united 
to a carboxyl group, COOH. By the union of ammonia and 
carbon dioxid the ammonium salt of this acid is formed, 

NH 2 

2 NH 3 + C0 2 = I 

COONH4 

Ammonium carbamate, is a constituent of commercial ammo- 
nium carbonate and an antecedent of ammonium carbonate in 
the hydrolysis of urea. 

Amino-acetic Acid, also called glycocoll and glycin, is obtained 
with other amino acids by boiling glue with either acids or 
alkalis.* It is also obtained, by the hydrolysis of glycocholic 
acid, from bile. 

Hippuric Acid (Plate V, Fig. 4) consists of benzoic acid 
united chemically to glycocoll, and may be produced syntheti- 
cally by the union of these two substances. 

Amino-valeric Acid, CH 2 (NH 2 )-(CH 2 ) 3 -COOH, may be ob- 
tained with glycocoll from elastin, the protein of the elastic 
fibres, of tendons, etc.f Isomeric with amino-caproic acid is 
leucin, an amino-isobutyl-acetic acid, J 

CH 3x 

CH-CH 2 -CH(NH 2 )-COOH. 
CHs 7 

Leucin is a cleavage product in the decomposition of proteins, 
including keratin and collagen. It results from the tryptic 

* Bernthsen, Organic Chemistry. 

t Foster, Chemical Basis of the Animal Body. 

% Novy, Physiological Chemistry. 



PLATE V.— ORGANIC CHEMISTRY. 




Fig. i. 
Iodoform. 




Fig. 3. 
Urea Nitrate. 





Fig. 4. 
Hippuric Acid. 




Fig. 5. 
Benzoic Acid (sublimed). 



Fig. 6. 
Tyrosin. 



ORGANIC ACIDS 223 

digestion of the hemipep tones and is regarded, as are other 
amino acids, as antecedent of urea (Plate V, Fig. 2). 

Cystin, C6H12N2S2O4, is an amino acid occasionally found in 
the urine in diseases where the sulphur compounds fail to be 
properly oxidized. It occurs under these circumstances as reg- 
ular colorless hexagonal plates (Plate X, Fig. 6) . 

By the oxidation of crystin and subsequent splitting off of 

C0 2 taurine is produced. 

CH 2 NH 2 

Taurine, (Amino-ethyl-sulphonic acid) I , results 

CH 2 (S0 2 OH) 
from the cleavage of protein, also from the decomposition of 
taurocholic acid from bile. 

Leucin, (CH 3 ) 2 .CH.CH 2 .CHNH 2 .COOH), is an a amino iso- 
butyl acetic acid and occurs usually with tyrosin as a decompo- 
sition product of protein (casein) . It is occasionally found in the 
urine as "leucin spheres" (represented in Plate V, Fig. 2). 

Tyrosin is a complex amino acid obtained from the decom- 
position of protein substances, particularly old cheese. It is oc- 
casionally found in urinary sediments as colorless needle-shaped 
crystals usually grouped as tufts or " sheaves." (Plate V, Fig. 6) . 

Dibasic Amino Acids. 

Of this class of compounds two may be mentioned: amino- 
succinic, aspartic or asparaginic acid, COOH-CH 2 -CH(NH 2 )- 
COOH, may be obtained from animal and vegetable proteins 
and in the pancreatic digestion of fibrin. 

Glutamic Acid is an amino-glutaric (pyrotartaric) acid, and 
occurs similarly to aspartic acid, except that it is not formed by 
pancreatic digestion. 

Laboratory Exercise LVI. 

Experiments with Organic Acids not of the C n H 2 n 2 Series. 

Exp. 84. To a dilute solution of permanganate of potassium 
add a few drops of sulphuric acid and heat nearly to boiling. 



224 ORGANIC CHEMISTRY 

Note if any change takes place. Now add a few crystals of ox- 
alic acid and watch carefully. Explain the use of sulphuric acid. 

Exp. 85. In separate test-tubes, insoluble oxalates may be 
produced by adding a solution of ammonium oxalate to a solu- 
tion of (a) calcium chlorid, (b) silver nitrate, (c) zinc sulphate, 
(d) copper sulphate, (e) lead nitrate. 

Exp. 86. Place in an ignition- tube, fitted with delivery- tube 
to collect evolved gas in test-tube, about 3 grams of dry calcium 
oxalate. Heat strongly and test gas evolved with lighted match 
or splinter. After ignition-tube has become cold add dilute 
H2SO4 and pass gas evolved into lime water. 

Exp. 87. Dissolve about 3 grams of dry oxalic acid (ioo° C.) 
in a test-tube half full of methyl alcohol. It will probably be 
necessary to boil the mixture before solution is complete and 
great care must be used to avoid burning of the alcohol. The 
use of a water-bath is recommended. As the hot mixture cools, 
dimethyloxalate will crystallize out. 

Separate sufficient of the crystals to obtain melting-point, 
which should be about 54 C. 

Exp. 88. The ester prepared in above experiment may be 
dissolved in alcohol and upon addition of NH 4 OH will give a 
precipitate of oxamid. 

Exp. 89. Take a test-tube half full of calcium chlorid (10%), 
make strongly alkaline with NH 4 OH and pass CO2 into the 
mixture for several minutes. A solution of calcium carbonate 
will result. 

Write reaction, CaCl 2 + 2 C0 2 + 4 NH 4 OH = ?. Heat the 
solution of calcium carbonate just produced till a precipitate of 
CaC0 3 is produced. 

Write reaction with one molecule of water on left-hand side 
of equation. 

Exp. 90. To 1/3 test-tube of cider vinegar add a few cubic 
centimeters of basic acetate of lead solution; a bulky precipitate 
of lead malate separates out. 



ORGANIC ACIDS 225 

Exp. 91. Dilute a few drops of neutral ferric chlorid solu- 
tion until no color is discernible, then to 10 c.c. of this dilution 
add 4 to 5 drops of 1/2% solution of lactic acid. A greenish- 
yellow color constitutes the test. 

In practical application of this test, it needs further con- 
firmation by boiling the unknown solution with a drop or two 
of HC1 and then extracting with ether. Evaporate the ether, 
take up the residue in 2 or 3 c.c. of water and repeat the test 
as given above. If the yellow color persists, it is due to lactic 
acid. 



CHAPTER XXV. 
AMINS OR SUBSTITUTED AMMONIAS. 

If one or more of the H atoms of ammonia, NH 3 , be replaced 
by a hydrocarbon group, the resulting compound is an amin; 
thus CH3-NH2 is methylamin, and (CH 3 ) 2 NH is dimethylamin. 
Trimethylamin, (CH 3 ) 3 N, has been found among the decom- 
position products of fresh brain, human liver, and spleen.* 
It is poisonous and possesses a strong, fishy odor. At ordi- 
nary temperature it is a gas, but, like ammonia, is freely soluble 
in H 2 and forms a variety of salts. 

Diamins are derived from two molecules of ammonia, as 
/NH 2 
ethylene diamin, C 2 H 4 

X NH 2 

To this class of compounds belong many of the "ptomains, " 
produced by the putrefaction of organic matter, as putrescin, 
(butylene diamin), CH 2 NH 2 -(CH 2 ) 2 -CH 2 NH 2 , and cadaverin, 
(penta-methylene diamin), CH 2 NH 2 -(CH 2 ) 3 -CH 2 NH 2 . A large 
number of the ptomains are aromatic compounds and as such 
will be referred to later. 

Amids. 

If the hydrogen of NH 3 be replaced by an oxygenated or 
acid radical, an amid results; thus NH 2 (C 2 H 3 0) is acetamid, 
or this compound may be regarded as acetic acid, CH 3 -COOH, 
in which the OH has been replaced by NH 2 . 

Formamid, CHO.NH 2 , is a liquid miscible with both alcohol 
and water. It boils with partial decomposition at about 200 C. 

* Vaughn and Novy, Cellular Toxins. 
226 



AMINS OR SUBSTITUTED AMMONIAS 227 

Upon heating quickly, it splits into CO and NH 3 . (Bernthsen.) 
Phenyl-formamid, CHO.NHC 6 H 5 , known as formanilid, occurs 
as yellow crystals soluble in water and in alcohol. 

Hydrazines. 

From diamid, NH 2 -NH 2 , or hydrazine, may be derived such 
substitution products as methyl-hydrazine, CH 3 -NH-NH 2 ; ethyl- 
hydrazine, C 2 H 5 -NH-NH 2 ; and phenyl-hydrazine, C 6 H 5 NH-NH 2 . 

This latter compound forms, with the monosaccharids and 
with many of the disaccharids, yellow crystalline compounds, 
known as osazones, which are precipitated in characteristic 
crystalline forms, recognizable upon microscopical examination 
and by their melting-points (see under Carbohydrates, page 260). 



CHAPTER XXVI. 
CYANOGEN COMPOUNDS. 

Cyanogen, C 2 N 2 , is an intensely poisonous gas, colorless, 
heavy (specific gravity 1.81), and inflammable. It is very 
easily soluble in water or alcohol, forming unstable solutions, 
which, upon decomposition, give rise to various nitrogen com- 
pounds, among them ammonia, hydrocyanic acid, and urea. 

Hydrocyanic Acid, HCN, may be produced by the fer- 
mentation of the glucoside amygdalin from bitter almonds; 
also from the kernel of peach-stones, cherry-laurel leaves, etc. 
HCN may be formed by direct synthesis of C 2 H 2 (acetylene) 
and nitrogen. The synthesis is induced by passing electric 
sparks through the mixed gases. It is conveniently prepared 
in the laboratory by distilling a mixture of dilute sulphuric 
acid with potassium ferrocyanide, K 4 Fe(CN) 6 + 5 H 2 S04 = 
6 HCN + FeS0 4 + 4 KHS0 4 . Hydrocyanic acid is a colorless, 
poisonous liquid, boiling at 26. 5 C, with a characteristic odor 
often designated as a peach-stone odor. It is soluble in H 2 0, 
and a 2% aqueous solution constitutes the acidum hydrocyani- 
cum dilutum of the pharmacopoeia, also known as prussic acid. 

Potassium Cyanide (KCN or KCy) occurs in trade as a white 
solid, sometimes granular, more often as a powder. It is in- 
tensely poisonous owing to the dissociation of the salt and activ- 
ity of the free cyanogen. 

KCN is decomposed by carbonic acid of the air with liber- 
ation of HCN. The aqueous solution of KCN hydrolyzes in 
two distinct ways: the most easily apparent at ordinary tem- 
perature is with the formation of HCN and KOH giving the 
solution an alkaline reaction: 

KCN + H 2 = HCN + KOH. 

228 



CYANOGEN COMPOUNDS 229 

Upon boiling a solution, the second hydrolysis may be dem- 
onstrated whereby NH 3 and potassium formate are produced: 

KCN + 2 H 2 = HCOOK + NH 3 (Exp. 96, page 230). 

The organic cyanids are known as nitrils or isonitrils, accord- 
ing as the hydrocarbon radical is attached directly to the C or 
to the N of the cyanogen group. That is, methyl cyanid would 
be represented by CH 3 -CN, while the isocyanid would be 
CH 3 -NC (methyl carbamin); the nitrogen atom being in the 
first place trivalent, in the second quinquivalent. 

Of these two classes of compounds, the isocyanids are of 
much greater interest to the student of dental medicine owing 
to their relation to the isocyanates and to urea. 

Phenyl-isocyanid, C 5 H 6 NC, also known as isobenzonitril, 
is produced by warming aniline (C6H 5 NH 2 ) with alcoholic 
potash and chloroform, the intensely disagreeable odor of 
which is utilized as a test for chloroform or chloral hydrate 
(page 167); or, with chloroform and potassium hydrate, the 
production of isocyanid may become a test for aniline, acetanilid 
(antifebrin), etc. 

Isocyanic Acid, O = C = N-H (carbimid), is supposed to be 
the acid of ordinary potassium and ammonium cyanates. 

Fulminic acid (C == N-O-H), isomeric with cyanic acid 
N = C-O-H and isocyanic acid (0 = C = N-H), is important 
only because of its relation to the fulminates, which are explosive 
compounds of the acid, with some of the heavy metals, such as 
Ag and Hg. 

Thiocyanic Acid or Sulphocyanic Acid. — In this acid and 
its salts, the atom of S replaces the oxygen of the cyanate in 
the empirical symbol (HCNS) ; but, graphically, the S is attached 
to the basic element (metal or H) rather than to C: thus, 
K-S-C = N, that is, the sulphocyanate is not an isocompound. 
For occurrence and relations of HCNS in the human body, see 
chapter on Saliva. 



230 ORGANIC CHEMISTRY 

Laboratory Exercise LVII. 
Experiments with Cyanogen Compounds. 

Exp. 92. In a test-tube dissolve 1/2 gram or less of potas- 
sium ferrocyanid in about 4 c.c. of H 2 0. Add a little H 2 S0 4 and 
boil, conducting the gas evolved into another test-tube by means 
of a bent glass tube. Note the odor of this dilute solution. 
(Do not smell of the contents of generating- tube, as the strong 
acid is intensely poisonous.) 

2 K 4 FeCy 6 + 6 H 2 S0 4 = K 2 Fe(FeCy 6 ) + 6 KHS0 4 + 6 HCy. 

Exp. 93. To one half of the dilute hydrocyanic acid prepared 
in the previous experiment add a drop or two of AgN0 3 solu- 
tion with a little HN0 3 . After the precipitate has settled, 
decant the fluid, then add an excess of ammonia- water. 

Exp. 94. To the other half of the HCy from Exp. 92 add a 
little solution of ferrous sulphate; also a few drops of ferric 
chlorid solution; then a little KOH solution; mix thoroughly 
and acidify with HC1. A blue precipitate, Fe 4 (FeCy 6 )3, is a test 
for HCy or any soluble cyanid. 

Exp. 95. To a few drops of KCN solution add a little 
yellow ammonium sulphid, (NH 4 ) 2 S, and evaporate to dryness. 
Dissolve in water; acidify with HC1 and add Fe 2 Cl 6 solu- 
tion. 

Exp. 96. In a small flask boil a solution of KCN. While 
boiling, test the vapors for ammonia gas. Solution of potassium 
formate remains in the flask. 

Complete reaction, KCN + 2 H 2 = ?. 

Exp. 97. To a little dilute (2%) solution of K 4 FeCy 6 add 
a little bromin water and boil. Prove the formation of K 3 FeCy 6 
by use of FeCl 3 . 

From this experiment what is the relative valence of iron in 
the two compounds ? Why ? 



CYANOGEN COMPOUNDS 231 

Exp. 98. To a fresh solution of K 3 FeCy 6 add a little 10% 
KOH solution and some PbO, shake and filter. To the clear 
filtrate add FeCl 3 . 

Give reason for the statement that the PbO has acted as a 
reducing agent. 



CHAPTER XXVII. 
UREA. 

This substance forms about 50% of the total solids and 
about 85% of the nitrogenous matter contained in the urine. 
When we consider that only 5% of the nitrogenous waste passes 
off in the feces and 95% in the urine, the importance of urea as 
an index of the nitrogen excreted and of protein metabolism 
becomes apparent. 

Urea was the first organic substance synthesized from in- 
organic compounds. This was accomplished by producing a mo- 
lecular rearrangement of ammonium isocyanate. The reaction 
is conveniently brought about by the double decomposition of 
potassium cyanate and ammonium sulphate and subsequent 
evaporation of the solution to dryness: 

2 CNOK + (NH 4 ) 2 SO = OCN.NH4 + K 2 S0 4 . 
Then O = C = N - NH 4 (ammonium isocyanate) + heat = 

/NH 2 

O = C (urea). 

X NH 2 

/OH 

Urea is the amid of carbonic acid, O = C , and from this 

x OH 
type may be explained the rapid transformation of urea into 

X NH 2 
ammonium carbonate in stale urine. = C with one 

X NH 2 
/ONH4 
molecule of H 2 becomes = C or ammonium carba- 

X NH 2 

mate, and this, by addition of a second molecule of water, be- 

232 



UREA 233 

/ ONH 4 

comes = C or ammonium carbonate, (NH 4 ) 2 C0 3 . The 

N ONH 4 
last part of the reaction takes place whenever commercial 
" ammonium carbonate" [really a mixture of carbamate 
(NH4-NH2-CO2) and acid carbonate (NH4HCO3)] is dissolved 
in water. 

Urea crystallizes in long needle-shaped crystals of the rhom- 
bic system. It is insoluble in water, somewhat soluble in 
alcohol, and nearly insoluble in ether. It fuses at 13 2 , and at 
a somewhat higher temperature it gives off ammonia and am- 
monium carbonate, and at 160 leaves a residue of ammelid, 
cyanuric acid, and biuret. Urea is decomposed by solutions of 
the alkaline hypochlorites or hypobromites being broken up into 
N, C0 2 , and H 2 0, as follows: 

CO(NH 2 ) 2 + 3 NaOBr = C0 2 + N 2 + 2 H 2 + 3 NaBr. 

Cyanuric Acid, (N3C3O3H3), is a polymer of cyanic acid 
(NCOH), which is, at first, formed in the above decomposition. 
/CO-NH2 

Biuret, H— N , may be obtained by heating urea. 

x CO-NH 2 
When pure, it occurs as white, needle-shaped crystals. With 
NaOH and 1% CuS0 4 it gives the characteristic violet and rose- 
red shades obtained in the biuret reaction (Piotrowski's proteid 
test). Exp. 157, page 277. 

Urea Nitrate may be precipitated from fairly concentrated 
urine by addition of HN0 3 . It separates in hexagonal crystals 
or plates, easily recognizable under the microscope (Plate V, 
Fig. 3, opposite page 222). 

Urea Oxalate. — Upon addition of a solution of oxalic acid 
to concentrated urine, crystals of oxalate of urea are precipi- 
tated. They are rather more easily obtained in characteristic 
forms (Plate II, Fig. 5, opposite page 162) than are the crystals, 
of nitrate, and, in consequence, treatment with oxalic acid con- 
stitutes a better method for the qualitative detection of urea in 



234 ORGANIC CHEMISTRY 

the body fluids than the nitric acid test formerly used. These 
crystals polarize light, and the use of the micropolariscope facili- 
tates their detection. 

Substituted Ureas. — The hydrogen of the amino group 
may be replaced by alcohol radicals forming what are known 

/HN 2 
as alkylated ureas; thus, = C is methyl urea, 



X NHCH, 



/NH 2 



O = C , ethyl urea, and one, two, three, or all four of 

X NHC 2 H 5 
the H atoms may be so replaced. 

When, in place of an alcohol radical, the acid radical is in- 
troduced, a class of compounds known as "ureids" results; thus, 
/NH 2 

o = c x 

NH(C 2 H 3 0) (acetyl urea). 

COOH 
In case of a dibasic acid, such as oxalic, I , entering 

COOH 
into the reaction, one or both (OH) groups may be split off, f orm- 

/NH 2 
ing in the first instance a ureid acid, as = C 

x NH.CO, COOH 
oxaluric acid, 

COOH /NH 2 y NH 2 

I +0 = C =0 = C +H 2 

COOH X NH 2 x NH-CO 

I 

COOH 
y NH-C = 
or, in the second case, a ureid, as O = C I parabanic 

X NH-C = 
acid. 

If the residue of two molecules of urea enter into the com- 
position of the new molecule, the compound is a diureid. Of 
this class one of the most important is: 



UREA 235 

Uric Acid, trioxypurin, C5H4N4O3. Its relation to urea may 

NH-CO 
I I 
be shown by the graphic formula = C C-NH X 



NH-C-NH ' 







Uric acid is also referable to a purely hypothetical base, "purin, " 
by the use of which the relationship of xanthin, hypoxanthin, 
and other "purin" or nuclein bases is easily demonstrated. 

These bases are of great physiological interest, in that they 
form an unquestioned link between the decomposition products 
of the proteins, nuclein, etc., on the one hand, and uric acid 
and the urates on the other. 

Purin is represented by the formula C 5 H 4 N 4 , or graphically 
N = C-H 
I I 
as H-C C-N-H . If we now break all double bonds ex- 
it II )C-H 
N - C-N^ 

cept those linking two carbon atoms (4 and 5), we obtain a 
1 - N-C 6 
I I 
graphic nucleus, 2 = C C 5 -N — 7 , by numbering the atoms 
I II )C = 8 
3 -N-C 4 -N-q 
of which we may easily designate any structural formula of the 
group; thus, 2-6-8, trioxypurin, is uric acid as above, while 

H-N-C = 
I I 
xanthin is 2-6, dioxypurin, O = C C-N-H , and 1-3-7, 

I II )C-H 
H-N-C-INr 
CH3-N-C = o 
I I 

trimethyl-xanthin, = C C — N — CH 3 , is caffein and thein, 

I II X C-H 

CH 3 -N-C-N^ 
alkaloids from coffee and tea. 



256 ORGANIC CHEMISTRY 

Traces of xanthin (2.6 dioxypurin) , hypoxanthin (6 oxy- 
purin), guanin (2 imino, 6 oxypurin), adenin (6 amino purin), 
and heteroxanthin (7 methyl xanthin) have been found in urine, 
and, in cases of leukaemia, many of them in increased amounts, 
notably xanthin, hypoxanthin, and adenin (Witthaus). 

Uric acid occurs in the urine ; there are traces of it in the blood ; 
and it is occasionally found, in the form of urates, in saliva. It 
is a dibasic crystalline acid, colorless when pure; but, in uri- 
nary sediment, it occurs generally as crystals, yellow to red, 
" whetstone "-shaped, and in various other forms (Plate X, Figs. 
1 and 2). The "brickdust" deposit occasionally found in urine 
consists of uric acid. It is insoluble in alcohol and nearly 
insoluble in water; but its solubility in water is increased by the 
presence of urea. 

Upon heating uric acid, urea and cyanuric acid may be ob- 
tained; NH 3 and C0 2 are given off. We are not to infer 
from this decomposition that the uric acid is an antecedent of 
urea in the animal body; for such is not the case, except possibly 
to a limited extent. 

Uric acid produces, upon oxidation, a variety of compounds, 
according to the temperature and the oxidizing agent employed. 

CI, hot, yields cyanuric acid, C3H 3 (OH) 3 . CI or Br, cold, 

. /NHCO x . 
forms oxalic acid, alloxan, (CO v .CO), parabanic acid, 

x NHCO / 

/ /NH-COV 

I CO I J, and ammonium cyanate. HN0 3 in the cold, 

\ x NH-CO/ 

forms alloxan, alloxantin, and urea (Witthaus). 

Uric acid may be detected by the murexid test. See Exp. 104, 
page 239. 

While uric acid is practically insoluble in H 2 and the acid 
urates only sparingly soluble, the uric acid in the system is 

Note. — Murexid is a definite chemical compound (CsHoNsOe) and may be 
produced from alloxantin, an oxidation product noted above. 



UREA 237 

apparently held in solution as an acid urate (NaHU) by the 
presence of the sodium phosphates, NaH 2 P0 4 and Na 2 HP0 4 , 
possibly also aided by the presence of some unknown organic 
combination. 

NaHU + NaH 2 P0 4 forms, at 3 8° C, a solution with an acid 
reaction; if, however, the mixture is cooled to room tempera- 
ture, the reaction becomes alkaline from Na 2 HP0 4 , and uric 
acid is precipitated (Bunge) : 

NaHU + NaH 2 P0 4 = Na 2 HP0 4 + H 2 U. 

Na 2 HP0 4 is a normal constituent of the blood, and a tendency 
to precipitate uric acid may be met by the following reac- 
tion : Na 2 HP0 4 + H 2 U = NaH 2 P0 4 + NaHU. Because the acid 
urate of lithium is much more soluble in water than any of the 
other monometallic urates, lithium salts have long been used as 
uric acid solvents. But the fact that lithium solutions will 
precipitate from solutions of Na 2 HP0 4 crystals of Li 2 HP0 4 , has 
been made the basis for a claim that such use of lithium salts is 
without effect other than to decompose and render insoluble 
the alkaline phosphate, which has been acknowledged a valu- 
able factor in keeping uric acid in solution. While the disodic 
phosphate is regarded by many as superior to lithium salts as 
a uric acid solvent, the fact of comparative insolubility of 
Li 2 HP0 4 can hardly be regarded as conclusive evidence that 
lithium compounds are not effective. 

The following in regard to our need for " sarsaparilla " in 
the spring is given by Dr. E. C. Hill, of the University of Den- 
ver, in his text-book of chemistry, page 370: " Reduced alka- 
linity of the blood, as in winter from eating meats freely, throws 
uric acid out of solution to collect in the more acid tissues (spleen, 
liver, and joints). With the vernal tide of alkalinity (due to 
freer sweating, with excretion of fatty acids) these deposits are 
swept out in the blood-current, irritating the nerves and giving 
rise to 'that tired feeling.'" 



2$S ORGANIC CHEMISTRY 

Laboratory Exercise LVIII. 
Urea and Uric Acid. 

Exp. 99. Make separate solutions of 10 grams of potassium 
cyanate * and 8.25 grams of ammonium sulphate. Mix and 
evaporate on a water-bath in a shallow dish. Separate the 
potassium sulphate as the evaporation proceeds; finally, evapo- 
rate to dryness and extract with absolute alcohol. Evaporate 
alcohol and reserve the urea for subsequent experiments. (See 
Urea, page 232.) 

Exp. 100. Heat a few crystals of urea in a test-tube until they 
fuse and no more gas is given off; cool, and dissolve the fused 
mass in water; add one or two c.c. of strong NaOH solution, 
then not more than one or two drops of a 1% CuS0 4 solution. 
Note the pink to violet color produced. This constitutes the 
biuret reaction used in physiological chemistry as a test for 
albumoses and peptones. Biuret is formed from urea as follows: 



NH 2 = C 



NIL 



/iN-n-2 



20 = <NH 2 = = C> H + NH3 ' 

X NH 2 

Exp. 101. Produce crystals of urea nitrate and oxalate 
(page 233) and examine under the microscope. Repeat with urea 
obtained from urine. 

This experiment may be performed by concentrating to 
about 1/5 its bulk a little urine and using the concentrated solu- 
tion as a solution of urea. 

Exp. 102. Treat 5 c.c. of urea solution (urine may be used) 
with a little sodium hypochlorite or hypobromite; note results 
and study reaction given on page 233. 

* For method of making potassium cyanate, see Preparation of Reagents and 
Organic Compounds, in the Appendix. 



UREA 239 

Exp. 103. Heat one-third of a test-tube of urine with barium 
hydroxid (baryta-water); test vapor with red litmus for NH 3 . 

Exp. 104. Murexid test for uric acid: Place a very small 
quantity of uric acid on a porcelain crucible cover, or in a small 
evapora ting-dish. Add two or three drops of strong nitric acid 
and evaporate to dryness over a water-bath. A yellowish-red 
residue remains, which changes to a purplish red upon addition 
of a drop of strong NH 4 OH, and purple -violet upon further 
addition of a drop of KOH solution, the color disappearing 
upon standing or upon the application of heat. (Difference 
from xanthin, which also gives a deeper red color.) 

Exp. 105. Repeal No. 104, using caffein in place of uric acid. 

Exp. 106. Heat a little sodium acid urate in a dilute solution 
of NaH 2 P0 4 . Allow to cool, and examine any deposit for uric 
acid crystals. Test reaction of solution both hot and cold 
(page 237). 

Exp. 107. Mix, and allow to stand for some time at reduced 
temperature, 30 c.c. of urine (a 2% urea solution), 2 or 3 c.c. of 
strong Na 2 C0 3 solution, and 5 c.c. of saturated NH 4 C1 solution. 

A precipitate consists of ammonium urate. 

Examine under the microscope and make murexid test. 



CHAPTER XXVIII. 
CLOSED-CHAIN HYDROCARBONS. 

In illustrating the simpler relationship of organic compounds 
we have, as far as possible, carefully avoided reference to the 
closed-chain or aromatic compounds, as the characteristic group- 
ings are more easily seen by the use of simple formulas. The 
distinguishing feature of the aromatic (also called cyclic) com- 
pounds is a nucleus consisting of a closed chain of atoms; this 
chain may contain three, four, five, six, or seven members, but 
the six-carbon ring is by far the most important, and the only 
one which we are to consider. 

The hydrocarbons of the aromatic series have, for a general 
formula, C n H 2n -6, the simplest being benzene or benzol, CeH 6 ; 
and we may consider that the aromatic compounds are derived 
from this. The structure of the benzene molecule is repre- 
sented by "Kekule's" benzene ring. Note that 
there are three double bonds, which of course . 

permit of addition products, as C 6 H 6 C1 2 , ben- q 

zene di-chlorid, etc. The substitution products tt_p C-H 
are, however, of far greater importance. | h 

Benzene, CeH6 (benzol), is a colorless liquid H-C C-H 
from the " light-oil" obtained by distillation of % C y 

coal-tar. It boils at 8o°, has a gravity of 0.899, ' 

is soluble in ether, alcohol, and chloroform, but 
insoluble in H 2 0. It may be made pure by ch^ tilling an inti- 
mate mixture of benzoic acid and quicklime, and at a temper- 
ature of about 5 C. may be obtained as a crystalline solid, 
C 6 H 5 COOH + CaO = CaC0 3 + C 6 H 6 . (See Exp. 108, page 
250.) 

240 



CLOSED-CHAIN HYDROCARBONS 241 

Toluene, C 7 H 8 (toluol). — The next higher homologue of the 
series will be C 7 H 8 ; this is methyl benzene, (C 6 H 5 CH 3 ), or 
toluene. 

The hydrocarbons of this series may be prepared in a manner 
similar to that used in the preparation of the hydrocarbons of 
the paraffin series. 

Toluene may be made by the action of metallic sodium upon 
a mixture of brombenzene and methyl iodid. 

C 6 H 5 Br + CH3I + Na 2 = C 6 H 5 CH 3 + NaBr + NaT 

Toluene is a colorless liquid boiling at no° C, and yielding 
upon oxidation a benzene derivative; i.e., the CH 3 , or so-called 
side chain, is the part of the compound changed by oxidizing 
agents rather than the benzene ring, 

C 6 H 5 CH 3 + 30 = C 6 H 5 C0 2 H + H 2 0. 

Xylene, C 8 Hi (xylol) or dimethylbenzene, the next hydro- 
carbon of this series, exists in coal tar as a mixture of three 
isomeric compounds which may be graphically represented as 
follows : 

CH 3 CH 3 CH 3 

Q CH3 Qch 3 and 

CH 3 

These three possible positions of the second substitution are 
known as ortho-, meta-, and para-; thus, the first representation 
at the left will be ortho-xylene, or ortho-dimethylbenzene. The 
other two will be meta-xylene and para-xylene respectively. 

A trisubstituted benzene may be " adjacent," if the sub- 
stituted element or group is attached to the carbon atoms 1-2-3 
or " unsymmetrical " (1-2-4) or "symmetrical" (1-3-5). 

A fourth isomer of dimethylbenzene would be an ethyl 
benzene, C 6 H 5 C2H 5 . This, upon oxidation, yields benzoic acid, 
a benzene derivative in a manner similar to toluene. 



242 ORGANIC CHEMISTRY 

Mesitylene, C9H12, is a trimethylbenzene. Only two isomers 
are possible. It can be prepared by dehydrating acetone by 
the use of sulphuric acid : 



3 C 3 H 6 - 3 H 2 = C 9 H 



■12. 



Derivatives of the Hydrocarbons of the Aromatic Series. 

The derivatives of the closed-chain hydrocarbons are very 
numerous, and many of them have very complex formulae. We 
shall confine our study to a few of the most simple and at the 
same time most common. 

The halogen derivatives are numerous and easily made, but 
are not of particular importance from a dental standpoint. 
The hydroxyl derivatives, on the other hand, are of great import- 
ance. The first is phenol. 

Phenol, carbolic acid, or oxybenzene, C 6 H 5 OH, obtained 
from the distillation of coal-tar, and used as an antiseptic and 
disinfectant. For properties and test, see page 174. Phenol 
acts like an acid, in that it forms salts with the metallic bases, 
C 6 H 5 OK, potassium phenolate, but it does not have an acid 
reaction on litmus paper or other indicators, i.e., it does not 
have free hydrogen ions when in solution, but belongs to the 
alcohols rather than the acids. 

The three di-hydroxybenzenes are all of interest and are 
graphically represented as follows: 

OH OH 



and 



I I U-tl benzene or i i benzene or 

pyrocatechol | QTT 



OH 

f I />ara-dihydroxy 

benzene or 
v / hydroquinol 

OH 



CLOSED-CHAIN HYDROCARBONS 243 

The ortho compound is pyrocatechol. Its ethereal sulphate 
(acid sulphate) is given by Hoppe-Seyler as a constituent of nor- 
mal urine, and its monomethyl ether, guaiacol, C 6 H 4 OH-0-CH 3 , 
is obtained from beech-wood creosote, of which it constitutes 
the greater part (60 to 90 per cent U. S. D.). Guaiacol and 
various compounds produced from it have been widely recom- 
mended for tubercular diseases. 

Pyrocatechol has been found to be the most practical reagent 
for the detection of oxydizing enzymes* in the saliva. 

Resorcinol is a white crystalline solid, becoming more or less 
colored upon exposure to the light. It melts at 118 C, and, 
in solution, gives a purple color with ferric chlorid. Heated 
with sodium nitrate, it produces a substance known as "Lacmoid" 
which is used to a considerable extent as an indicator. 

The hydroquinol or hydrochinon, is a white powder melt- 
ing at 169 C, and is largely used as a photographic developer. 

Trihydroxybenzene, or pyrogalol, C 6 H 3 (OH) 3 (1-2-3), mav 
be made by heating gallic acid, and because of this fact is usu- 
ally called pyrogallic acid. It is a white silky crystal which, 
like hydroquinol, is used as a photographic developer. Dis- 
solved in a solution of caustic potash it absorbs oxygen to a 
marked degree, and may be used as a reagent for the quantita- 
tive determination of oxygen in gas analysis. 

Phloroglucinol is another trihydroxybenzene, isomeric with 
pyrogalol but with the hydroxyl groups occupying positions 
1-3-5 in the ring. The formula is C 6 H 3 (OH) 3 (1-3-5). 

It crystallizes in rhombic prisms, soluble in water, alcohol 
and ether. This is used in physiological chemistry as a reagent 
with vanillin as a test for free hydrochloric acid. 

Thymol (3methyl-6 isopropyl-phenol) , C 6 H 3 OH (l) CH 3(3) C 3 H 7(6) , 
is a solid of the nature of camphor, melting at 44 C, and is 
obtained from various volatile oils, particularly from the oil 
obtained from Thymus Vulgaris. It is very sparingly soluble in 

* Journal of the Allied Societies, Vol. 4, page 346. Dec, 1909. 



244 ORGANIC CHEMISTRY 

water. The addition of a little alcohol increases the solubility. 
It is largely used in the preparation of antiseptic dental prepa- 
rations, mouth washes, etc. 

Phenol-sulphonic Acid. — When phenol is treated with 
several times its volume of cold, strong H 2 S0 4 , phenol sulphonic 

OH OH 

acid, r 1HSO3 or ( 1 results. If the mixture is heated for 

\/ \/ 

HSO3 

some time over a water-bath, the disulphonic acid results. This 
acid, warmed with a nitrate and the mixture treated with excess 
of ammonia, yields ammonium picrate, and constitutes a delicate 
test for nitrates present in drinking-water. 

Phenol-sulphonic acid has been used in dentistry as a 
therapeutic agent (as antiseptic and otherwise). Such use is 
discussed in detail by Herman Prinz, M.D., D.D.S., in the 
Dental Cosmos for April, 191 2, with the conclusion that the 
ortho compound is several times more active than either the 
meta or para compounds: that a 1 per cent solution is about 
equal in antiseptic strength to a 1 per cent phenol solution, but 
in this strength it decalcifies the tooth structure, discolors the 
teeth, and should not be used in the mouth on account of its 
pronounced acid character. 

Sulphonic Acids as a class may be obtained by the oxidation 
of an organic sulphydrate (mercaptan). This oxidation may 
be produced by the action of HN0 3 or KMn0 4 , and may be 
written as follows: 

C 2 H 5 SH + 3 = C 2 H 5 .S0 2 .HO. 

Compounds of this class are not confined to the hydro- 
carbons of the aromatic series as the above typical reaction 
shows. 

Aromatic sulphonic acids may be made by a similar process : 

C 6 H 5 SH + 30 = C 6 H 5 S0 2 HO, 



CLOSED-CHAIN HYDROCARBONS 245 

and also by the action of sulphuric acid or the hydro- 
carbons. 

Sulphons are oxidation products of organic sulphids: as, 

C 2 H 5x y/ 
or example, ethyl sulphone S 

Mercaptan, an organic sulphydrate. Representatives of this 
class of compounds are found as derivatives of both the open 
and the closed-chain hydrocarbons. 

Ethyl mercaptan, also called thioalcohol, C2H5SH, is a type 
of this class. It is a colorless liquid used in the preparation of 
sulphonal. 

The mercaptans may be prepared by action of KHS on the 
alkyl haloids: 

C2H5CI + KHS = C2H5SH + KC1. 

Taurine is an important sulphonic acid of the parafhn 
series. Its graphic formula shows it to be an amino ethyl sul- 

/HSOs 
phonic acid C 2 H 4 . Taurine is derived from taurocholic 

N NH 2 
acid by hydrolysis. This acid is representative of one of the two 
principal acid groups occuring in the bile, the salts of which may 
be found in pathologic conditions in the urine, or, according to 
Dr. J. P. Michaels and others, in the saliva. 

Nitro-benzene, C 6 H 5 N02, may be produced by treating ben- 
zene with a mixture of nitric and sulphuric acid at reduced 
temperature. (Exp. no, page 251.) It is a yellow, oily liquid, 
with the odor of bitter almonds, commercially known as oil of 
mirbane, and used in the manufacture of aniline. 

Phenyl Sulphuric Acid, C 6 H 5 HS04, occurs only in combina- 
tion, the acid being unstable if attempt is made to isolate it. 
Its potassium salt is present in the urine as a product of in- 
testinal putrefaction. 



246 ORGANIC CHEMISTRY 

Aniline or Amino-benzene, C 6 H 5 NH 2 . By reaction of nitro- 
benzene with nascent hydrogen, the N0 2 group becomes an NH 2 
group and aminobenzene or aniline is produced. Aniline, a color- 
less liquid, also called aniline oil, is important from a commercial 
rather than from a medical standpoint, as it forms the basis of 
the aniline dyes. When pure it is a colorless liquid, but changes 
quite rapidly when exposed to the light. It is used in testing for 
chloral and chloroform. It is slightly soluble in water, and 
easily soluble in alcohol and ether. At 8° C. it becomes a crys- 
talline solid. 

Cresol, C3H4CH3OH, is a hydroxy- toluene. Three isomeric 
compounds of this formula are obtained from the distillation of 
coal tar between 200 and 210 C. The ortho and para cresols are 
solid at ordinary temperatures, the ortho compound melting at 
31 C, the para at 3 6° C. Meta cresol is a liquid which does 
not solidify unless under extreme conditions of cold and pressure. 

The cresols are similar to phenol not only in composition but 
also in physical and therapeutic properties ; hence, cresol has been 
called cresylic acid, just as phenol has been called carbolic acid. 

A mixture of the cresols, said to be composed of meta cresol 
40%, ortho 35%, and para cresol 25%, constitutes the tricresol 
very largely used in dentistry as a germicide and antiseptic sim- 
ilar to carbolic acid. 

An emulsion of cresol, obtained by the solution of resin soap 
as an emulsifying agent, is known as creolin. Cresol is also a 
constituent of the disinfectant lysol. 

Tricresol is miscible with formalin in all proportions, and the 
mixture is recommended in the treatment of root canals. 

Picric Acid is trinitrophenol, C 6 H 2 .OH.(N0 2 )3. It may be 
formed by action of strong HN0 3 , or mixture of H 2 S0 4 and 
HNO3 on phenol. It occurs as yellow plates slightly soluble 
in H 2 0, easily soluble in alcohol and ether, and is used in Esbach's 
reagent for the estimation of albumin in urine and as an alkaloidal 
precipitant. 



CLOSED-CHAIN HYDROCARBONS 247 

Benzoic Acid, C 6 H 5 COOH, was originally produced from gum 
benzoin, but may be made from hippuric acid (q. v.), which 
(from urine of horses) formerly constituted a commercial source. 
It is chiefly prepared, however, from toluene; it crystallizes 
in colorless plates or long prismatic crystals (from solution). 
It is sparingly soluble in cold water, more soluble in hot water, 
easily soluble in alcohol. It sublimes and is inflammable, burn- 
ing without residue. 

Benzoates of sodium, ammonium, lithium, and lime are all 
used in medicine. Benzoated lard is prepared by digesting gum 
benzoin in hot lard. This is much used as a base for ointments 
and keeps well. 

Benzaldehyd, C 6 H 5 -CHO, is a colorless liquid, soluble in 
alcohol and ether, and sparingly soluble in water. The U. S. P. 
oil of bitter almonds is practically benzaldehyd; it is a volatile 
oil, very poisonous, and upon standing deposits benzoic acid 
from partial oxidation. 

Salicylic Acid, orthohydroxybenzoic acid, C 6 H 4 -OH.COOH, 
is a white crystalline powder, odorless, irritating to mucous sur- 
faces, soluble in alcohol and ether, and in about 450 parts of 
water at 15 C. (U. S. D.). Salicylic acid may be made by 
action of C0 2 on sodium phenate and subsequent decomposition 
of the sodium salicylate. By heating rapidly the acid may be 
changed into phenol and C0 2 . 

Salicylates have been used to considerable extent in various 
uric-acid diseases. Methyl salicylate constitutes 90% of natu- 
ral oil of wintergreen (page 207). The alcoholic solution is 
essence of checkerberry. 

Salol is phenylsalicylate, CeH^OH.COCKCeHs), a white 
crystalline powder, practically insoluble in water and not de- 
composed by the dilute acids of the stomach juices; but in the 
intestine it becomes salicylic acid and phenol, as follows: 

C 6 H 4 .OH.COOC 6 H5 + H 2 = C 6 H 4 OH.COOH + C 6 H 5 OH. 



248 ORGANIC CHEMISTRY 

/HS0 3 
Sulphanilic acid, C 6 H 4 , is isomeric with taurine, but 

X NH 2 

is obtained, however, from an entirely different source. It is 
made by treating aniline with concentrated sulphuric acid. It 
is a strong acid, occurring as white crystals, is soluble in water, 
and is used in the manufacture of aniline dyes and also with 
naphthylamin as a reagent for the detection of nitrites. 

/COOH 
Phthalic acid, C 6 H 4 , occurs in the form of rhombic 

x COOH 
crystals. By heating phthalic acid, phthalic anhydrid may be 
obtained. 

/ co \ 

Phthalic anhydrid, C 6 H 4 O, heated with phenol and 

H2SO4 will give phenolphthalein, a valuable and familiar indi- 
cator in volumetric analysis. 

Hippuric Acid, benzoyl glycocoll, C 6 H 5 .CO.NH.CH 2 -COOH, 
occurs in traces in human urine, to a considerable extent in 
the urine of the herbivora, but not at all in that of the car- 
nivora. It crystallizes in prismatic needles (Plate V, Fig. 4), 
often resembling crystals of ammonium magnesium phosphate; 
but as these latter only occur in neutral or alkaline urine and 
hippuric acid, usually in acid urine, there is little danger of 
confounding the two substances. Hippuric acid is hydrolyzed 
by the urease of fermenting urine, forming benzoic acid and 
glycocoll (amino-acetic acid) : 

C 6 H 5 CO-NH-CH 2 -COOH+H 2 

= C 6 H 5 COOH+CH 2 NH 2 COOH. 

Tryosin, C 6 H 4 .OH.-CH 2 CH(NH 2 )-COOH, may be crystal- 
lized as fine silky needles. It is formed from protein sub- 
stances, particularly casein and fibrin, both by the action of 
proteolytic enzymes and by putrefactive processes. It rarely 



CLOSED-CHAIN HYDROCARBONS 249 

occurs in urinary sediment; when found it is in bundles or 
sheaves (Plate V, Fig. 6, page 222), and is usually indicative of 
acute liver disease, phosphorus poisoning, etc. 

Heterocyclic Compounds. — The closed-chain or cyclic com- 
pounds are known as isocyclic or homocyclic when the atoms 
constituting the "ring" or nucleus of the molecule are all of 
the same sort (carbocyclic, if all of carbon), as has been the case 
in all the aromatic compounds which we have thus far taken 
up, i.e., the structure of compounds has been based upon the six- 
carbon or benzene ring. If the ring is made up of atoms of 
different sorts the compound is heterocyclic, and one or two of 
these are of importance. 

First, pyridin, C5H5N, which may be regarded as benzene, in. 
which one CH group has been replaced by an atom of nitrogen : 

H 

/\ 

HC CH 

I II 
HC CH 

It is a liquid miscible with water, boiling-point 115 C. 
Second, quinalin, C9H7N, a colorless liquid. 

H H 

// C x// C x 
HC C CH 

I I II 

HC C CH 

H 

Upon one or the other of these two bases may be constructed 
the graphic formula of many of the vegetable alkaloids. 

A certain number of alkaloids, such as caffein and thein (tri- 
me thy lxan thin), are referable to the purin nucleus (page 235). 



250 ORGANIC CHEMISTRY 



H 



HC C CH 

Indol, C 8 H 7 N, — I II II , — is produced from pro- 

HC C CH 

H H 

tein by the putrefaction occurring in the small intestine, also by 
action of the proteolytic enzyme of the pancreatic juice (trypsin) . 
The indol, by oxidation (after absorption from the intestines), 
becomes indoxyl, C 8 H 6 NO, which, with K 2 S0 4 , forms indoxyl- 
potassium sulphate, C 8 H 6 NKS0 4 , and, as such, is eliminated (in 
part) by the kidneys. This substance is a type of the so-called 
ethereal or conjugate sulphates, skatoxyl-potassium sulphate 
(skatol) and phenol-potassium sulphate being other com- 
pounds of this class. The ethereal sulphates are not precipi- 
tated by BaCl 2 in alkaline solutions, but may be decomposed by 
prolonged boiling with HC1 and then precipitated as usual. 

The oxidation of indoxyl produces indigo blue, and this fact 
is utilized in the qualitative test for indoxyl in urine (q. v.). 

y C.CH3 ^ 

Skatol, methylindol, C 6 H 4 N / CH, occurs in similar 

\NH/ 

manner to indoxyl, and likewise passes into the urine as an 
ethereal sulphate (skatoxyl-potassium sulphate). Skatol is a 
constituent of the feces and possesses a strong fecal odor. 

Laboratory Exercises LIX and LX. 
Experiments with Aromatic Hydrocarbons. 

Exp. 108. Into a small and thoroughly dry flask (250 c.c.) 
introduce about 50 grams of a mixture consisting of 1 part of 
benzoic acid and 2 parts of quicklime ; connect with a condenser 
and heat. Benzene (benzol) distils over: 

CaO + C 6 H 5 COOH = CaC0 3 + C 6 H 6 . 



CLOSED-CHAIN HYDROCARBONS 251 

Exp. 109. Turn a little of the benzene prepared in the last 
experiment onto some water contained in a porcelain capsule. 
Set fire to it and note that it burns with a smoky flame. Cool a 
few cubic centimeters of pure benzene contained in a narrow 
test-tube by immersion in a freezing mixture of ice and salt. 

Exp. no. In a wide test-tube mix 5 c.c. of concentrated 
H 2 S0 4 with about half its volume of strong HN0 3 ; cool in ice- 
water or cold running water, and add very slowly about 2 c.c. 
of benzene. Nitrobenzene is formed and may be separated as 
a heavy oily liquid by pouring the mixture into an excess of 
water. Notice the odor of oil of bitter almonds. 

Exp. in. Observing the same precaution against overheat- 
ing as given in Exp. no reduce nitrobenzene to amino benzene 
as follows: In a large test-tube or small flask place 1 or 2 c.c. 
of nitrobenzene with three times its weight of tin powder. To 
this add 10 or 15 c.c. of strong HO in successive small portions, 
keeping cool as indicated. The odor of nitrobenzene should be 
replaced by that of aniline. 

Exp. 112. Shake together in a test-tube 1 part of aniline oil 
and 5 parts of water. Is the oil soluble in water? 

Agitate with HC1 added in small portions till liquid becomes 
clear. Explain. 

Exp. 113. To a few cubic centimeters of a 3% phenol solu- 
tion add dilute bromin water. A yellowish-white crystalline 
precipitate of tribromphenol is produced (see page 174). 

Exp. 114. To an aqueous solution of phenol add a few 
drops of solution of ferric chlorid. 

Exp. 115. Produce a tribromaniline according to method 
given for tribromphenol in Exp. 113. 

Exp. 116. Repeat Exps. 113 and 114, using an aqueous solu- 
tion of cresol in place of phenol. 

Exp. 117. To a test-tube 1/3 full of nitric acid, (50% abso- 
lute HNO3), add, 1 drop at a time, about 1 c.c. of phenol with 
constant agitation. When the phenol has all been added heat 



252 ORGANIC CHEMISTRY 

carefully to boiling. Allow to cool slowly when trinitrophenol 
will be precipitated. 

Exp. 118. Evaporate a few drops of a i% solution of potas- 
sium nitrate to dryness in a small porcelain capsule. Add 2 c.c. of 
phenoldisulphonic acid ; * stir thoroughly, and keep hot for three 
to five minutes; dilute with water, make strongly alkaline with 
ammonia, and note the intense yellow color of ammonium picrate. 
The reaction is used as a test for nitrates in drinking water. 

Exp. 119. Determine melting-point of benzoic acid. 

Exp. 120. Arrange two watch glasses of equal size with the 
concave surfaces together and a piece of filter paper stretched 
between them. The glasses may be held together with a small 
brass clamp. 

A little benzoic acid placed in the lower glass may be sub- 
limed by means of a gentle heat through the paper and collected 
upon the upper glass. Examine the sublimate by polarized 
light. See Plate V, Fig. 5, opposite page 222. 

Exp. 121. With an aqueous solution of benzaldehyd deter- 
mine whether Tollen's test for aldehyds (Exp. 64, page 201) is 
applicable to aromatic compounds. 

Exp. 122. Boil 10 c.c. of oil of wintergreen with a little of 20% 
NaOH; keep the volume constant by frequent addition of water. 
When the oil has entirely disappeared, cool and add HC1 to acid 
reaction. Salicylic acid will separate, white and crystalline. 

Exp. 123. To a dilute solution of sodium salicylate, or satu- 
rated aqueous solution of salicylic acid, add a few drops of 
Fe 2 Cl 6 . A slight amount of salicylates in the urine will produce 
this color when a test is being made for diacetic acid (q. v.) 

Exp. 124. Mix in a test-tube a little dry slaked lime and 
salicylic acid, heat and collect a few drops of distillate in a 
second tube. Test distillate for phenol. Write reaction. 

Note. — After the first heating, the tube containing the lime and acid may be 
inclined so that any moisture distillate will run into collecting tube rather than 
back onto the mixture. 

* For method of preparation of phenoldisulphonic acid, see Appendix. 



PART VI. 

PHYSIOLOGICAL CHEMISTRY. 



CHAPTER XXIX. 

FERMENTS OR ENZYMES. 

Physiological chemistry treats of the substances which go 
to make up the animal body, the changes which these substances 
undergo in the process of digestion and assimilation, and the final 
products of metabolism. 

This subject, like others, will receive our attention in out- 
line, with a view simply to enable the student to understand 
the conditions which at present seem to have the most direct 
bearing on dental science. The changes produced by the class 
of bodies known as ferments are of great importance and the 
first to be considered. 

If yeast is allowed to grow in a sugar solution of moderate 
strength, the sugar molecule is split into carbonic-acid gas and 
alcohol. The process is one of fermentation; the yeast is the 
ferment. There are various substances which cause similar 
splitting of complex molecules into simpler compounds.* 

The distinction between the organized and the unorganized 
ferments is no longer recognized, as it has been proved that the 
activity of an organized ferment is due to the presence of the 
unorganized ferment or enzyme, and we shall, by preference, 
refer to these substances as enzymes. 

The enzymes, as a class, possess certain general properties 
which should be remembered. 

* Occasionally fermentation may produce a synthesis (putting together) rather 
than an analysis (pulling apart). 

253 



254 PHYSIOLOGICAL CHEMISTRY 

First. Their action is limited to a very few substances; 
i.e., the enzyme from yeast, referred to above, will convert a 
few sugars only as indicated. They will not act in any other 
way nor upon other substances. 

Second. The enzymes act only at ordinary temperatures, 
usually showing the greatest activity at about the temperature 
of the animal body, 37 to 40 C. 

Third. Enzymes act only within very narrow limits as re- 
gards the chemical reaction (acid or alkaline) of the media. 

Fourth. Enzymes are destroyed (killed) by the heat of boil- 
ing water. 

Fifth. In regard to the nature of their composition, many of 
the enzymes are closely allied to the proteins. 

An enzyme may be classified according to the sort of work 
it does. Many of the chemical changes involved in the utiliza- 
tion of food consist of breaking up a complex molecule and by 
the use of a molecule of water forming new and simpler com- 
pounds. This sort of change is called "Hydrolysis" and an 
enzyme which will produce it is a hydrolytic enzyme. By 
hydrolysis or hydrolytic cleavage, the molecule of cane-sugar, 
C12H22O11, becomes two molecules of a simpler sugar, such as 
glucose, C 6 Hi 2 6 . Ci 2 H 22 0ii + H 2 = 2 C 6 Hi 2 6 . 

Hydrolysis is not dependent upon enzyme action, as the 
same change is produced by prolonged boiling with very dilute 
mineral acids. 

Besides the classification of enzymes by the character of the 
work they do, the name of the substance acted upon may also 
be used to designate an enzyme; thus, a proteolytic enzyme 
produces a cleavage of protein substances. A lipolytic enzyme 
(lipase) splits the fat molecule, etc. 

Several of the digestive enzymes, notably the proteolytic or 
flesh-digesting enzymes, such as pepsin, trypsin, etc., exist in 
the animal cell, not as active agents, but as inactive parent 
enzymes which are called pro-enzymes or zymogens. Enzymes 



FERMENTS OR ENZYMES 255 

of this class are set to work (liberated from the parent sub- 
stance) by a class of substances known as ' ' activators " (illus- 
trated by the enterokinase of the intestine, p. 337). 

Neither the zymogen nor the activator has of itself any diges- 
tive action whatever. A provision which results in the preven- 
tion of autodigestion (autolysis) of the cells containing them. 

Another large and very important class of enzymes are those 
which produce oxidative changes. They may be divided into 
the oxidases, which produce direct oxidation, and the peroxidases, 
which produce oxidation only in the presence or by the aid of 
peroxide. 

Catalase is a term which has been applied to enzymes, 
similar in action to the peroxides; i.e., they destroy a peroxide 
with the formation of molecular oxygen, although, according to 
Hammarsten, they differ from both the oxidases and peroxidases 
in giving no reaction whatever with Guaiac. 

Oxidases have been found to exist in saliva, in milk, blood, 
nasal mucus, tears, and semen, in many of the organs, and also 
in the muscular tissue. They exist moreover in the vegetable 
kingdom from which the subject of oxidizing enzymes was first 
studied by Bertrand and Bourquelot.* The urine, bile and intes- 
tinal secretions are said not to contain a ferment of this kind. 

The name of a specific enzyme usually ends in "-ase" as 
zymase, the enzyme contained in yeast; lipase, a fat-splitting 
enzyme; urease, the urine ferment. 

Laboratory Exercise LXI. 

Preparation of Oxidase. 

Exp. 125. Clean thoroughly a small potato and grate the 
skin into a small beaker; cover with water and allow to stand 
in a cool place for an hour. Filter through coarse paper. Turn 

*" Enzymes and their Applications," Effrant: Prescott's translation. This 
work is also authority for statement immediately preceding regarding the source 
of oxydizing enzymes. 



256 



PHYSIOLOGICAL CHEMISTRY 



about 5 ex. of the nitrate slowly into 25 c.c. of strong alcohol. 
The enzyme will be precipitated. Filter and test as follows : 

Exp. 126. Transfer the moist precipitate from the above ex- 
periment into a half a test tube of distilled water. Shake fre- 
quently for about 10 minutes and filter. The nitrate will con- 
tain oxidizing enzymes in solution. Divide the solution into 
two parts; to one add a few drops of tincture of guaiacum, and 
to the other a little of a 1% solution of pyrocatechol. The 
guaiacum gives a blue color, and the pyrocatechol a red-brown 
color in the presence of oxidizing enzymes. 

Experiments with Enzymes. 

Hydrolytic enzymes produce cleavage of the molecule. 

Exp. 127. Take five test tubes, " a-b-c-d-e." Make a 

thin paste by rubbing one-sixth of 
a yeast cake with water, and place 
a little in each of the five tubes; 
then fill "a" with a dilute glucose 
solution; a b " with a dilute solution 
of milk sugar; "c" with dilute 
solution of cane sugar; to "d" 
add a little invertase (an enzyme 
from the mucosa of the small in- 
testine of a pig) (see Appendix); 
then fill with the same solution 
used for "c". Prepare "e" ex- 
actly the same as u d" except that 
before adding the sugar solution 
the enzymes are boiled for at least 
one minute. Fit each tube with 
short delivery tube and allow to 
stand overnight. 




Arrange as indicated in Fig. 16. Explain result in each case. 
Exp. 128. Take four test-tubes, u a-b- 



-c-d," 



and half fill 



FERMENTS OR ENZYMES 257 

each with some thin starch paste (see page 383 of Appendix). 
Into "a" put a little of the yeast from last experiment; into 
"b" a little pepsin solution; into "c" a little saliva (the enzyme 
of the saliva in ptyalin); into u d" a little invertase as used in 
preceding experiment. Warm all the tubes to about 37 or 
38 C, and allow to stand overnight; then test contents of 
each tube for a reducing sugar which may have been produced 
from the starch. (Use Exp. 136, page 262). 

Exp. 129. If time and sufficient material are available, the 
student may prepare a fat-splitting enzyme (lipase) from an 
animal source, pigs, pancreas,* or from a vegetable source, castor 
beans.* 

Exp. 130. To one-third of a test-tube of milk, colored 
slightly blue with nearly neutral litmus solution, add half as 
much solution of lipase (fresh pancreatic extract) and keep at 
about 40 C. for twenty to thirty minutes. Sufficient fat acid 
should be separated to change the blue litmus to red. Write 
reaction. 

* For preparation of lipase see Appendix, pages 380 and 381. 



CHAPTER XXX. 



CARBOHYDRATES. 



Classification : r Arabinose 
Xylose 



Sugars 



Pentoses. 



Starch 



Dextrose 

Laevulose [• Monosaccharids or monoses. 

Galactose j 

Saccharose "1 

Maltose V Disaccharids or dioses. 

Lactose J 
( Starch 
( Glycogen 

Polysaccharids or polyoses. 

Dextrin 



Gum 
Cellulose 



Characteristics. — The monosaccharids are reducing bodies of 
either the aldehyd or the ketone type. The termination "ose" 
is applied to all sugars, and may also be used in designating the 
type; thus dextrose is an "aldose, " while laevulose is a "ketose;" 
i.e., dextrose is an aldehyd, containing the characteristic -CHO 
group, while Laevulose is a ketone containing the -C = 
group. 

The pentoses (C 5 Hi O 5 ) are represented by two important 
compounds, arabinose and xylose. The first of these occurs 
occasionally in the urine (pentosuria), and can be prepared by 
boiling gum arabic with dilute mineral acids. The second, 
xylose, has been obtained from the pancreas, but may be pre- 
pared more easily from bran or straw by boiling with dilute 
HC1 (Exp. 131, page 261). 

258 



CARBOHYDRATES 259 

The pentoses, as a class, boiled with dilute mineral acid 
(HC1 or H2SO4), yield furfuraldehyd by splitting off the elements 
of three molecules of water: 

C 5 H 10 O 5 - 3 H 2 = C 5 H 4 2 . 

The formation of furfuraldehyd can be easily demonstrated 
by various color reactions as given in experiment 131, page 261. 

The hexoses, C 6 Hi 2 6 , also called monoses, occur quite gen- 
erally in nature (not true of the pentoses). They constitute the 
various fruit sugars, and may be obtained by hydrolysis of the 
dioses and polyoses. 

They all reduce Fehling's copper solution (galactose less 
easily than the others), and they are all fermented by yeast 
(galactose more slowly than the others). 

Dextrose or Glucose, C 6 Hi 2 6 , also known as grape-sugar 
and as diabetic sugar, occurs in grapes, honey, etc. It is formed 
by the action of diastatic ferments on the disaccharids ; also 
from many of the polysaccharids. Glucose thus occurs in the 
processes of digestion and constitutes the sugar of diabetic 
urine. It may be obtained commercially as a white solid, and 
also as a thick, heavy syrup, known as confectioners' glucose. 
The commercial glucose is prepared by the action of dilute acids 
on starch, when hydrolysis takes place, as follows: 
C6H10C5 -f- H 2 = CeHi 2 06. 

Dextrose can be oxidized first to gluconic acid (CH 2 OH.- 
(CHOH) 4 .COOH), and by further oxidation to dibasic sac- 
charic acid: 

COOH.(CHOH) 4 .COOH. 

This oxidation can be effected by the use of nitric acid. Sac- 
charic acid forms a definite soluble salt with calcium. Whether 
the fact has any bearing whatever on the relation of poor teeth 
and excessive use of candy has not been demonstrated. 

Tests. — Glucose boiled with Fehling's solution precipitates 
the red suboxid of copper (Cu 2 0). 



260 PHYSIOLOGICAL CHEMISTRY 

Glucose responds to Molisch's test for carbohydrates, which 
is made with an alcoholic solution of a-naphthol and concen- 
trated sulphuric acid. (Exp. 133.) It may be distinguished 
not only from other carbohydrates but from other sugars by 
heating with Barfoed's solution (copper acetate in dilute acetic 
acid) , which is reduced with precipitation of Cu 2 0. 

Heated with phenylhydrazine solution nearly to the boiling- 
point of water, glucose forms phenylglucosazone, which crystal- 
lizes, as the mixture cools, in characteristic yellow needles 
usually arranged in bundles or sheaves. (Plate VI, Fig. 1.) 

Osazones are the various compounds formed by the different 
sugars and phenylhydrazine when treated as above. They 
crystallize in fairly distinctive forms and furnish valuable tests 
for the sugars. The phenylhydrazine test is considered at least 
ten times more delicate than Fehling's test. Glucose readily 
undergoes alcoholic fermentation, yielding C 2 H 5 OH and CO2. 
(See Exp. 140, page 262.) 

Laevulose, C 6 Hi 2 6 , or fruit-sugar, turns the ray of polarized 
light to the left, and to a greater degree than glucose turns it to 
the right. It occurs in honey and in many fruits, and is pro- 
duced with glucose by hydrolysis of cane-sugar. Laevulose 
forms an osazone not to be distinguished from glucosazone. It 
reduces copper solutions in a manner similar to glucose, and, like 
it, is easily fermented by yeast. 

Galactose is the product of the hydrolysis of lactose, or milk- 
sugar, and some other carbohydrates. It is a crystalline sub- 
stance which reduces Fehling's solution and ferments slowly 
with yeast. 

DlSACCHARTDS OR DlOSES. 

Disaccharids have the general formula C12H22O11. They 
are converted into the monosaccharids by hydrolysis brought 
about either by action of enzymes or by boiling with mineral 
acid. 



PLATE VI. — PHYSIOLOGICAL CHEMISTRY 





Fig. i. 

Glucosazone. 



Fig. 2. 
Maltosazone. 




Fig. 3. 
Lactosazone. 





Fig. 4. 
Wheat Starch. 




Fig. 5. 
A, Corn starch; B, Rice starch. 



Fig. 6. 
A, Potato starch; B, Arrowroot starch. 



CARBOHYDRATES 261 

Cane-sugar, C12H22O11, sucrose or saccharose, obtained from 
the sugar-cane (various varieties of sorghum), also from the 
sugar-beet (Beta vulgaris) and the sugar-maple (Acer saccha- 
rinum). Cane-sugar is a white crystalline solid soluble in about 
1/2 part of water and in 175 parts of alcohol (U. S. P.). It does 
not reduce copper solutions, nor does it form an osazone with 
phenylhydrazine ; but it is easily hydrolyzed with the formation 
of dextrose and laevulose, and then, of course, the reactions 
peculiar to these substances may be obtained. It does not fer- 
ment directly, but, by the action of invertin contained in yeast, 
it takes up water, becoming glucose and laevulose as above, these 
latter sugars being easily fermentable. 

Maltose, C12H22O11, or malt-sugar, is an intermediate prod- 
uct in the hydrolysis of starch, and by further hydration be- 
comes two molecules of dextrose: C12H22O11 + H 2 = 2 C 6 Hi 2 6 . 
It is formed in the fermentation of barley by diastase (the fer- 
ment of malt), and with phenylhydrazine it produces an osazone 
distinguished from glucosazone and lactosazone by its micro- 
scopical appearance (Plate VI, Fig. 2) and its melting-point. 

Lactose, C12H22O11, obtained from milk, is a disaccharid 
with far less sweetening power than sucrose. It forms an 
osazone which crystallizes in small burr-shaped forms (Plate VI, 
Fig. 3). It reduces Fehling's solution, but does not reduce 
Barfoed's solution. It resists fermentation in a marked de- 
gree. Upon hydration it is converted into dextrose and galac- 
tose. 

Laboratory Exercise LXII. 

Experiments with Sugars. 

Exp. 131. Fill a test-tube about one-third full of dry straw. 
Cover with 10% hydrochloric acid; boil, collecting the distillate 
in a dry tube. Divide the distillate into two parts, and make 
the following tests for furfuraldehyd which has been produced 
from the pentose contained in the straw. Treat the contents 



262 PHYSIOLOGICAL CHEMISTRY 

of one tube with a little aniline and HC1. Red coloration indi- 
cates the presence of furfuraldehyd. To the contents of the 
other tube add a little solution of casein (skimmed milk) and un- 
derlay with strong sulphuric acid. Furfurol will give a blue or 
purple line at the point of contact of the two liquids. 

Monosaccharids. — Exp. 132. Test for C and H, using cane- 
sugar. Make closed-tube test for H, which is given off as H 2 0, 
and for C, which remains as such in tube. (See page 182.) 
Write reactions. 

Exp. 133. Molisch's Test for Carbohydrates. — To a few 
cubic centimeters of a 3% glucose solution add a few drops of 
an alcoholic solution of a-naphthol, and carefully underlay the 
mixture with strong H 2 S0 4 . 

Exp. 134. To a few cubic centimeters of CuS0 4 solution 
in a test-tube add a little NaOH. Boil and write reaction. 

Exp. 135. Repeat Exp. 134 with the addition of Rochelle 
salt; if solution remains clear on boiling, add a few drops of a 
glucose solution. 

Exp. 136. Fehling's Test for Sugars. — Take about 5 c.c. of 
Fehling's solution* made by mixing equal parts of the CuS0 4 
solution and the alkaline tartrate on side shelf. Boil and add 
immediately a few drops of glucose solution. Set aside for a 
few minutes, watching the results. 

Exp. 137. Repeat Exp. 136, using diabetic urine instead of 
glucose. 

Exp. 138. Repeat Exp. 136 without heat and allow to stand 
for twenty-four hours. 

Exp. 139. Barfoed's Test. — To about 5 c.c. of Barfoed's 
reagent add a few drops of glucose solution; boil and set aside 
for a few minutes, watching results. 

Exp. 140. Fermentation Test. — Fill the " fermentation- 
tube" (Fig. 17, page 263) found in the desk with glucose solu- 
tion; add a little yeast; insert stopper, with long arm of tube 

* For preparation, see Appendix. 



CARBOHYDRATES 



263 



extending into glucose mixture nearly to bottom of tube, and 
allow it to stand upright, in a warm place, overnight. On the next 
day, test the gas, with which the tube is filled, with lime-water. 

Exp. 141. Phenylhydrazine Test. — Place about 5 c.c of 
glucose solution in a test-tube; add an equal 
volume of phenylhydrazine solution; keep the 
tube in boiling water for thirty minutes. Allow 
to cool gradually. Examine the precipitate micro- 
scopically and sketch the crystals. 

Disaccharids. — Exp. 142. Use dilute solu- 
tions of cane-sugar, milk-sugar, and maltose, 
and make on each Fehling's test (Exp. 136), 
Barfoed's test (Exp. 139), and the phenylhy- 
drazine test (Exp. 141). Sketch the different 
osazone crystals obtained. 

Exp. 143. To a dilute solution of cane-sugar 
add a few drops of dilute H 2 S0 4 and boil for 
five minutes. Cool the mixture and make slightly 
alkaline with NaOH. With this solution perform 
Exps. 136-139 and 141. Explain results. Com- 
pare with Exp. 142. 

POLYOSES — POLYSACCHARIDS. 




Fig. 17. 



Starch. — This well-known and widely distributed plant-con- 
stituent is a carbohydrate represented by C 6 Hi O5, the actual 
molecule, however, being many times this simple formula. The 
microscopical appearance of the starch granule is quite charac- 
teristic, and recognition of the more common starches by this 
method is not at all difficult (see Plate VI, page 261). 

Starch is not soluble in cold water, but in hot water, or in 
solutions containing "amylolytic" enzymes, or in solutions 
containing certain chemical substances, as chlorid of zinc or of 
magnesium, dilute HC1 or H 2 S0 4 , capable of forming hydrolytic 
products, the starch granules swell up, and ultimately dissolve, 



264 PHYSIOLOGICAL CHEMISTRY 

being converted into dextrose. The conversion, however, takes 
place in several well-dehned steps, as follows: Soluble starch 
is first formed, answering the same chemical test with iodin 
(Exp. 214, p. 328); next, erythrodextrin, which gives a red color 
with iodin solution; then achroo- and maltodextrin, which give no 
color with iodin, but react slightly with Fehling's copper solu- 
tion; then maltose, also negative with iodin, but reacting strongly 
with Fehling's solution; and finally dextrose. 

Dextrin (C6H10O5) is a yellowish powder, also known as 
British gum; is formed from starch, as indicated above; con- 
stitutes to a considerable extent the "crust" of bread; is solu- 
ble in water, the solution giving a red color with iodin, and is 
also distinguished from starch by its failure to give a precipitate 
with solution of tannic acid. 

Glycogen, or animal starch, is a carbohydrate, with the gen- 
eral formula C 6 Hi O5, occurring principally in the liver, and to 
a lesser extent in nearly all parts of the animal body. Freshly 
opened oysters are a convenient source of the substance for 
laboratory demonstration. It occurs in horse-flesh in consider- 
ably larger proportions than in human flesh. 

Properties. — Glycogen is a white powder without odor or 
taste. It dissolves in water, producing an opalescent solution. 
It is closely allied to the starches of vegetable origin in that the 
products of its hydrolysis are dextrin* and ultimately dextrose. 
It differs in its ready solubility in water, and in the fact that 
it is precipitated by 66% alcohol, also in its power of rotation, 
which is much stronger than that of starch. 

Physiology. — Glycogen is formed by the liver, and stored by 
this same organ for future use. It is derived principally from 
carbohydrates, but may also be derived from proteins. It dis- 
appears during starvation. In dead liver or muscle it rapidly 
undergoes hydrolytic change with the production of a reducing 
sugar. 

* Foster's Text-book of Physiology. 



CARBOHYDRATES 265 

Cellulose, C 6 Hi O5, is a carbohydrate which occurs as a 
principal constituent of woody fiber, and which may be found 
in the laboratory in nearly a pure state, as absorbent cotton 
or Swedish filter-paper. It is insoluble in water, alcohol, or 
dilute acids; it may be dissolved, however, by an ammoniacal 
copper solution. It is converted into monosaccharids by acids, 
only after first treating with concentrated H 2 S0 4 , which par- 
tially dissolves it. Cellulose aids digestion in a purely mechan- 
ical way; treated with a mixture of nitric and sulphuric acids, 
it is converted into nitro-substitution products which are known 
as guncotton. The soluble cotton from which collodion is pre- 
pared is a mixture of tetra- and pentanitrates, while the more 
explosive but insoluble guncotton is a hexanitrate, formerly 
known as trinitrocellulose. 

Experiments with Starches and Cellulose. 

Polysaccharids. — Exp. No. 144. Examine potato, corn, and 
wheat starch under the microscope, use a drop of water and a 
cover glass. Sketch the granules of each in note-book, and, 
while still on the slide, treat with a dilute iodin solution. Note 
changes in appearance of granules. 

Exp. 145. Preparation of starch. Grate a little raw potato. 
Mix thoroughly with water and strain through " bolting" cloth 
or stout coarse muslin. After the liquid has run through, com- 
press the cloth by twisting till no more liquid can be squeezed 
out. The starch has passed through the cloth and may be washed 
by decantation, dried on filter paper, examined, and used for 
the following experiments: 

Exp. 146. Make some starch paste by rubbing 1 gram of 
starch to a smooth, thin paste with water; then slowly pour it 
into 100 c.c. of boiling water, stirring constantly. With this 
solution compare a 1% solution of dextrin and a solution of 
glycogen * as follows : 

* For the isolation of glycogen, see Appendix. 



266 PHYSIOLOGICAL CHEMISTRY 

(a) Treat each by boiling with Fehling's solution. 
{b) Add to 5 c.c. of each a few drops of tannic-acid solu- 
tion. 

(c) To each solution add a drop of iodin solution. Note 
color of mixture while cold. Heat nearly to boiling and allow 
to cool again, watching the color during process. 

(d) To 5 c.c. of each solution add twice its volume of 66% 
alcohol. 

(e) Tabulate results of the tests and formulate method of 
distinguishing these three substances from one another. 









CHAPTER XXXI. 

FATS AND OILS. 

Natural fats and oils of animal or vegetable origin are 
mixtures of several compound glyceryl ethers or esters (see page 
209), and by subjecting them to cold and pressure they may 
be separated into two portions, one solid with comparatively 
high melting-point, and the other liquid at ordinary tempera- 
tures. The solid portion is known as the stearopten, and the 
liquid as the eleopten, of the fat. Thus from beef-fat we may 
express a fluid eleopten consisting largely of olein and obtain 
as a residue a stearopten, stearin. The stearopten of the vol- 
atile or. essential oils are classed as camphors, on account of 
their resemblance to ordinary camphor. Menthol, from oil of 
peppermint, and thymol, from oil of thyme, are examples of this 
class of compounds, both of which are largely used in dental 
practice. 

Properties. — Fats are insoluble in water, easily dissolved by 
ether, chloroform, and carbon disulphid, less easily by alcohol, 
crystallizing on evaporation of the solvent. (Plate VII, Fig. 3, 
page 296.) They are emulsified by mechanical subdivision of 
the fat globules, in the presence of some agent which prevents 
their reuniting. The vegetable mucilages, soap, jelly, etc., are 
such emulsifying agents. On exposure to the air, fats and oils 
are more or less easily oxidized, which causes a separation of the 
fat acid. This produces an unpleasant odor or taste, and the 
fat is said to become rancid. (For saponification of fats see 
page 209 and Exp. 150, page 268.) 

Physiology. — Fats are not digested to any appreciable ex- 
tent until they reach the intestine; here they are broken up 
by a fat-splitting enzyme, emulsified, and to a slight extent 

267 



268 PHYSIOLOGICAL CHEMISTRY 

saponified, after which they may be absorbed by the system 
(see Pancreatic Digestion). 

Experiments with Fats and Oils. 

Exp. 147. Test solubility of olive-oil in water, ether, chloro- 
form, and alcohol, carefully avoiding the vicinity of a flame. 

Exp. 148. Let one or two drops of an ether solution of the 
oil drop on a plain white paper, also an ether solution of a volatile 
oil found on side shelf. Watch behavior of the two oils, and 
report differences, if any. 

Exp. 149. Dissolve a little butter in warm alcohol, examine 
with the microscope, and micropolariscope the crystals, which 
separate on cooling. 

Note. — If possible perform the next experiment in triplicate, i.e. carry three experiments along 
at the same time using for " fat " the Glyceryl ester of the three most common fat acids: Olein 
(lard oil or olive oil), Stearin (beef fat or tallow), Palmatin (bayberry wax or tallow, which contains 
a large amount of free palmitic acid) . 

Exp. 150. Saponification. — To about 2 grams of solid fat 
placed in a narrow beaker, or 150 c.c. Erlenmeyer flask, add 10 
or 15 c.c of alcoholic solution of potassium hydroxid. Allow 
the beaker to stand on the water-bath till the alcohol is entirely 
evaporated, then dissolve the resulting soap in water; filter, if 
necessary, to obtain a clear solution and make the following tests : 

(a) Add to a portion of solution a saturated solution of 
sodium chlorid. What takes place ? 

(b) To another portion add a few cubic centimeters of a so- 
lution of calcium or magnesium chlorid. Explain the results. 

(c) Pour the remainder slowly, and with constant stirring, 
into warm dilute H 2 S0 4 , and heat on the water-bath. What is 
the result ? Write the equation. Transfer the mixture to a filter- 
paper which has been moistened with hot water, and wash with 
hot water till all H 2 S0 4 is removed. Reserve the filtrates. 

Exp. 151. Fatty -acids. 

(a) Dissolve a portion of the above precipitates (150 c) by 
warming with strong alcohol. Test the reaction of the solution. 



FATS AND OILS 269 

Examine the crystals, which separate upon standing, with micro- 
scope and micropolariscope. (Plate VII, Fig. 3, page 296.) 

(b) Add to a portion a few cubic centimeters of a strong 
Na2C03 solution, and heat till the fatty acids dissolve. Cool. 
What takes place? Explain the reaction. Reserve the jelly. 

Exp. 152. Neutralize the filtrates of 146 c and evaporate 
almost to dryness on the water-bath. Extract with alcohol 
and evaporate. Note the taste. Heat another portion of the 
residue with a little powdered dry KHS0 4 in a dry test-tube, 
and note the odor, which is due to acrolein, CH 2 = CH-CHO. 
Fuse some borax and glycerin on a platinum loop: green color. 

Exp. 153. Emulsification. — (a) Put 1 to 2 c.c. of a solution 
of sodium carbonate (0.25%) on a watch-glass, and place in 
the center a drop of rancid oil. The oil-drop soon shows a 
white rim, and a white milky opacity extends over the solution. 
Note with the microscope the active movements in the vicinity 
of the fat-drop, due to the separation of minute particles of oil 
(Gad's experiment). 

(b) Take six test-tubes and arrange as follows : 

1. 10 c.c. of a 0.2% Na 2 C0 3 solution + 2 drops of neutral 

oil. 

2. 10 c.c. of a 0.2% Na 2 C03 solution + 2 drops of rancid 

oil. 

3. 10 c.c. of soap-jelly (see 151 b), warm, + 2 drops of 

neutral oil. 

4. 10 c.c. of albumin solution + 2 drops of neutral oil. 

5. 10 c.c. of gum-arabic solution + 2 drops of neutral oil. 

6. 10 c.c. of water + 2 drops of neutral oil. 

Shake all the mixtures thoroughly and note the results. 
What conclusions do you form relative to the influence of con- 
ditions upon emulsification? 

(c) Examine a drop of an emulsion under the microscope. 



CHAPTER XXXII. 

PROTEINS. 

Protein * is a general term used to designate the nitrogenized 
bodies which constitute the greater proportion of animal tissue. 

While meat and " protein" are usually associated, it must 
not be forgotten that meat is not the exclusive source of protein, 
for we usually find protein in vegetable substances and often to 
a considerable extent. 

Unlike the two other great divisions of food substances (carbo- 
hydrates and fats), the structure of the protein molecule is so 
complex that with a few exceptions of the simplest kind its 
representation has not been attempted. 

The protein molecule contains nitrogen (often as the amino 
group NH 2 ) in addition to the C, H, and of the carbohydrates 
and fats. It frequently contains sulphur, often phosphorus, 
and occasionally the metallic elements, particularly iron. 

As examples of the complexity of protein molecules, the 
following proposed formulae are given in Hawk's Physiologi- 
cal Chemistry. 

Serum albumin, C450H720N116S6O140. 

Oxyhemoglobin, C 6 58Hii 8 iN207S 2 Fe02io. 

While a classification of proteins according to their chemical 
composition is at present practically impossible, the following 
may be of interest. 

After Hofmeister, Ergebnisse der Physiologie, Jahrg. I. 

* The term Proteid was formerly used instead of Protein, but in accordance 
with the recommendations of the Committees of the American Physiological and 
Biochemical Societies, it has been abandoned. The classification and definitions 
herewith given are taken from their recommendation as printed in Science, Vol. 
27, Xo. 692, page 554. 

270 



PROTEINS 271 

I. Groups of the Aliphatic Series. 

A. Group containing C, N, H. 

The only representative known is the guanidin radical 
(CNH).NH 2 . 

B. Groups containing C, N, H, 0. 

1. Amino-acids. 

(a) Monamino-acids. 

1. Monobasic monamino-acids, C n H 2n - f -iN0 2 . 

C 2 is glycocoll. 

C3 is alanin. 

C 5 is amino valerianic acid. 

C 6 isleucin, which occurs universally. 

2. Dibasic monamino-acids, C n H 2n _iN04. 

C4 is asparaginic acid. 
C5 is glutaminic acid. 

(b) Diamino-acids (all monobasic acids). 

C 2 is diaminoacetic acid (rare). 
Argynin (guanidin-a-aminovalerianic acid) . Here the 
diamino-acid is combined with the guanidin radical, 

NH 2 .NH.C.NH.CH 2 .(CH 2 ) 2 .CH.NH 2 COOH. 

Lysin (a-e-diaminocapronic acid), 

NH 2 .CH 2 .(CH 2 ) 3 .CH.NH 2 .COOH. 

2. Amino-alcohols. 

Glucosamin, C 6 Hn0 5 (NH 2 ), a hexose into which 
NH 2 has entered the carbohydrate group of the 
protein molecule. 

C. Groups containing C, N, H, 0, S. 

Cystein,aminothiolacticacid,CH 2 .SH.CH(NH 2 ).COOH. 
Cystin, the sulphid of cystein, CeHi 2 S 2 N 2 04. 
a-thiolactic acid. 



27a PHYSIOLOGICAL CHEMISTRY 

II. Groups of the Aromatic Series. 

A. Phenylalanin, C 6 H 5 .CH 2 .CH(NH 2 ).COOH. 

B. Tyrosin, C 6 H 4 .OH.CH 2 .CH(NH 2 ).COOH. 

III. 

A. Pyrrol group. 

CH-CH-CH-CH.COOH 

1 . a-pyrrolidin carbonic acid, I 



NH 



B. Indol group. 

1. Indol, see page 250. 

2. Skatol (methyl indol), see page 250. 

3 . Tryptophan (indolaminopropionic acid) , CnHi 2 N 2 2 . 

4. Skatosin, Ci Hi 6 N 2 O 2 . 

C. Pyridin group. 

Pyridin, see structural formula on page 249. 

D. Pyrimidin group. 

Histidin: structural formula probably 

NH CH 

I II 

CH = C - N - CH 2 - CHNH 2 - COOH. 

Excepting the carbohydrate group, and perhaps the pyridin 
and pyrimidin groups, which are absent in a few special in- 
stances, all typical proteins contain at least one representative 
from each group. 

A much more practical classification, based in part upon the 
properties of the substance, is that suggested by the Joint Com- 
mittees on Protein Nomenclature (footnote, page 270). 

" Since a chemical basis for the nomenclature of the proteins 
is at present not possible, it seems important to recommend 
a few changes in the names and definitions of generally accepted 
groups, even though, in many cases, these are not wholly 
satisfactory." The recommendations are as follows: 



PROTEINS 273 

First. The word proteid should be abandoned. 

Second. The word protein should designate that group of 
substances which consists, so far as is known at present, essen- 
tially of combinations of a-amino acids and their derivatives, 
e.g., a-aminoacetic acid or glycocoll; a-amino propionic acid or 
alanin; phenyl-a-amino propionic acid or phenylalanin; guan- 
idin-amino valerianic acid or arginin, etc., and are therefore 
essentially polypeptids. 

Third. That the following terms be used to designate the 
various groups of proteins : 

I. Simple Proteins. 

Protein substances which yield only a-amino acids or their 
derivatives on hydrolysis. 

Although no means are at present available whereby the 
chemical individuality of any protein can be established, a 
number of simple proteins have been isolated from animal and 
vegetable tissues which have been so well characterized by con- 
stancy of ultimate composition and uniformity of physical 
properties that they may be treated as chemical individuals 
until further knowledge makes it possible to characterize them 
more definitely. 

The various groups of simple proteins may be designated as 
follows : 

(a) Albumins. — Simple proteins soluble in pure water and 
coagulable by heat; e.g., ovalbumin, serum albumin, lactalbumin, 
vegetable albumins. 

(b) Globulins. — Simple proteins insoluble in pure water, but 
soluble in neutral solutions of salts of strong bases with strong 
acids;* e.g., f serum globulin, ovoglobulin, edestin, amandin, and 
other vegetable globulins. 

* The precipitation limits with ammonium sulphate should not be made a 
basis for distinguishing the albumins from the globulins. 

f The examples of the various proteins are those given by Prof. P. B. Hawk. 



274 PHYSIOLOGICAL CHEMISTRY 

(c) Ghdclins. — Simple proteins insoluble in all neutral 
solvents but readily soluble in very dilute acids and alkalies;* 
e.g., glutenin. 

(d) Alcohol-soluble Proteins (Prolamins). — Simple proteins 
soluble in relatively strong alcohol (70 to 80 per cent), but in- 
soluble in water, absolute alcohol, and other neutral solvents;! 
e.g., zein, gliadin, hordein, and bynin. 

(e) Albuminoids. — Simple proteins which possess essentially 
the same chemical structure as the other proteins, but are 
characterized by great insolubility in all neutral solvents;! e.g., 
elastin, collagen, keratin. 

(J) Histories. — Soluble in water and insoluble in very dilute 
ammonia and, in the absence of ammonium salts, insoluble even 
in an excess of ammonia; yield precipitates with solutions of 
other proteins and a coagulum on heating which is easily soluble 
in very dilute acids. On hydrolysis they yield a large number 
of amino acids, among which the basic ones predominate; e.g., 
globin, thymus histone, scombrone. 

(g) Protamins. — Simpler polypeptids than the proteins in- 
cluded in the preceding groups. They are soluble in water, un- 
coagulable by heat, have the property of precipitating aqueous 
solutions of other proteins, possess strong basic properties and 
form stable salts with strong mineral acids. They yield com- 
paratively few amino acids, among which the basic amino acids 
greatly predominate; e.g., salmine, sturine, clupeine, scombrine. 

* Such substances occur in abundance in the seeds of cereals and doubtless 
represent a well-defined natural group of simple proteins. 

f The sub-classes defined {a, b, c, d) are exemplified by proteins obtained from 
both plants and animals. The use of appropriate prefixes will suffice to indicate 
the origin of the compounds, e.g., ovoglobulin, myoalbumin, etc. 

| These form the principal organic constituents of the skeletal structure of 
animals and also their external covering and its appendages. This definition does 
not provide for gelatin, which is, however, an artificial derivative of collagen. 



PROTEINS 275 

II. Conjugated Proteins. 

Substances which contain the protein molecule united to 
some other molecule or molecules otherwise than as a salt. 

(a) Nucleo proteins. — Compounds of one or more protein 
molecules with nucleic acid; e.g., cystoglobulin, nucleohistone. 

(b) Glycoproteins. — Compounds of the protein molecule 
with a substance or substances containing a carbohydrate group 
other than a nucleic acid; e.g., mucins and mucoids (osseomu- 
coid, tendomucoid, ichthulin, helicoprotein) . 

(c) Phospho proteins. — Compounds of the protein molecule 
with some, as yet undefined, phosphorus- containing substance 
other than a nucleic acid or lecithins;* e.g., caseinogen, vitellin. 

(d) Hemoglobins. — Compounds of the protein molecule with 
hematin or some similar substance; e.g., haemoglobin, haemo- 
cyanin. 

(e) Lecitho proteins. — Compounds of the protein molecule 
with lecithins (lecithans, phosphatids) ; e.g., lecithans, phos- 
phatids. 

III. Derived Proteins. 

1. Primary Protein Derivatives. — Derivatives of the pro- 
tein molecule apparently formed through hydrolytic changes 
which involve only slight alterations of the protein molecule. 

(a) Proteans. — Insoluble products which apparently result 
from the incipient action of water, very dilute acids or enzymes ; 
e.g., myosan, edestan. 

(b) Metaproteins. — Products of the further action of acids 
and alkalies whereby the molecule is so far altered as to form 
products soluble in very weak acids and alkalies, but insoluble 
in neutral fluids. 

* The accumulated chemical evidence distinctly points to the propriety of 
classifying the phosphoproteins as conjugated compounds; i.e., they are possibly 
esters of some phosphoric acid or acids and protein. 



276 PHYSIOLOGICAL CHEMISTRY 

This group will thus include the familiar "acid proteins" and 
"alkali proteins,' 1 not the salts of proteins with acids; e.g., acid 
metaproteins' (acid albuminate), alkali metaprotein (alkali 
albuminate). 

(c) Coagulated Proteins. — Insoluble products which result 
from (1) the action of heat on their solutions, or (2) the action 
of alcohols on the protein. 

2. Secondary Protein Derivatives* — Products of the further 
hydrolytic cleavage of the protein molecule. 

(a) Proteoses. — Soluble in water, uncoagulated by heat, and 
precipitated by saturating their solutions with ammonium sul- 
phate or zinc sulphate; f e.g., protoproteose, deuteroproteose. 

(b) Peptones. — Soluble in water, uncoagulated by heat, but 
not precipitated by saturating their solutions with ammonium 
sulphate; { e.g., antipeptone, amphopeptone. 

(c) Peptids. — Definitely characterized combinations of two 
or more amino acids, the carboxyl group of one being united 
with the amino group of the other, with the elimination of a 
molecule of water; § e.g., dipeptids, tripeptids, tetrapeptids, 
pentapeptids. 

Laboratory Exercise LXIII. 

General Protein Reactions. 

Exp. 154. Test dried egg-albumin for C, H, S, and N, ac- 
cording to the methods described on pages 182 and 183. Test 
casein for phosphorus, and dried blood for iron. 

* The term secondary hydrolytic derivatives is used because the formation of the 
primary derivatives usually precedes the formation of these secondary derivatives. 

f As thus defined, this term does not strictly cover all the protein derivatives 
commonly called proteoses; e.g., heteroproteose and dysproteose. 

% In this group the kyrins may be included. For the present we believe that 
it will be helpful to retain this term as defined, reserving the expression peptid 
for the simpler compounds of definite structure, such as dipeptids, etc. 

§ The peptones are undoubtedly peptids or mixtures of peptids, the latter term 
being at present used to designate those of definite structure. 



PROTEINS 277 

There are several reactions which are common to nearly all 
proteins. For the following tests use a solution of egg-albumin 
(1/50) in water, as a general type of a protein. 

1. Color Reactions. 

Exp. 155. Xanthoproteic Test. — To 10 c.c. of the albumin 
solution add one third as much concentrated HN0 3 ; there may 
or may not be a white precipitate produced (according to the 
nature of the protein and the concentration). Boil; the pre- 
cipitate or liquid turns yellow. When the solution becomes 
cool add an excess of NH 4 OH, which gives an orange color. 
(This color constitutes the essential part of the test.) 

Exp. 156. Milton's Test. — Add a few drops of Millon's re- 
agent * to a part of the albumin solution. A precipitate, which 
becomes brick-red upon heating, forms. The liquid is colored 
red in the presence of non-coagulable protein or minute traces 
of albumin. 

Exp. 157. PiotrowskVs Test. — To a third portion add 2 
drops of a very dilute solution of CuS0 4 , and then 5 to 10 c.c. 
of a 40% solution of NaOH. The solution becomes blue or 
violet. Proteoses and peptones give a rose-red color (biuret 
reaction) if only a trace of copper sulphate is used; an excess 
of CuS0 4 gives a reddish-violet color, somewhat similar to that 
obtained in the presence of other proteins. This test responds 
with all proteins. 

2. General Precipitants. 

Proteins are precipitated from solution by the following re- 
agents (peptones are exceptions in some cases) : 

Exp. 158. Acetic Acid and Potassic Ferrocyanid. — Make 
part of the solution to be tested strongly acid with acetic acid, 

* Mercuric nitrate in nitric acid. For the preparation of this and other reagents, 
see Appendix. 



278 PHYSIOLOGICAL CHEMISTRY 

and add a few drops of potassic ferrocyanid solution. A white 
flocculent precipitate is formed (not with peptones). 

Exp. 159. Alcohol. — To another part add one or two vol- 
umes of alcohol. 

Exp. 160. — Tannic Acid. — Make the solution acid with 
acetic acid, and add a few drops of tannic-acid solution. 

Exp. 161. Potassio-nier curie Iodid. — Make acid another 
portion with HO, and add a few drops of the reagent. 

Exp. 162. Neutral Salts. — Certain neutral salts precipitate 
most proteins. (NH 4 ) 2 S0 4 added to complete saturation to 
protein solutions, faintly acid with acetic acid, precipitates all 
proteins, with the exception of peptones. 

Simple Proteins. 
Albumins. 

The albumins are conveniently represented by egg-albumin 
and serum-albumin. They are soluble in water, respond to the 
general protein reactions (Exp. 155, page 277, etc.), and may be 
completely precipitated by saturation of the solution by am- 
monium sulphate. Albumin is coagulated by heat (7 5 to 8o° C .) . 

Egg-albumin differs from serum-albumin in that it is not 
absorbed when injected into the circulation, but appears un- 
changed in the urine. Egg-albumin is readily precipitated from 
aqueous solution by alcohol, while serum-albumin is precipi- 
tated only with difficulty. Albumins in general form, with 
acids or with alkalies, derived albumins known as acid or alkali 
albumins or albuminates (acid or alkali metaproteins) . An acid 
albumin derived from myosin is known as syntonin. It differs 
but slightly from other acid albumins. The acid and alkali 
albumins are both precipitated by neutralization, but neither of 
them are coagulated by heat. 

If the hydrolysis of albumin is brought about by HC1 at the 
body temperature, it causes the molecule to split into two 



PROTEINS 279 

proteins, one known as antialbuminate and the other as hemi- 
albumose, these in turn becoming respectively antialbumid and 
hemipeptone. Sulphuric acid at a boiling temperature produces 
a similar change, except that the hemipeptone is further changed 
to leucin and tyrosin. Digestive ferments, pepsin, and trypsin 
produce antialbumose, hemiantipeptone, and hemialbumose, 
but trypsin alone converts the hemipeptone into leucin and 
tyrosin. 

Albumin normally occurs in all the body fluids except in the 
urine. The amount in milk is extremely slight; the amount in 
saliva seems to vary in inverse proportion to mucin. Albumin 
occurring in urine in appreciable quantity is always abnormal, 
although in many cases it has no serious significance unless 
persistently present in more than the slightest possible trace. 

Globulin occurs in both plants and animals, and crushed 
hemp seed may be used as a convenient source for laboratory 
experiment. It is also associated with albumin in blood-plasma, 
and may be separated from it by half saturation with ammonium 
sulphate, which precipitates the globulin only, but it is not to 
be distinguished by the ordinary protein tests and reactions. 
The albumin of albuminous urine always consists of a mixture 
of these two proteins, globulin and albumin, not, however, al- 
ways in the same proportion. The globulins are not soluble in 
distilled water as the albumins are, but a very small quantity of 
neutral salt, such as sodium chlorid, will serve to effect the solu- 
tion. Globulin is thrown out of solution by action of carbon 
dioxid as a white flocculent precipitate. By dialysis the in- 
organic salts necessary for its solution will be removed and the 
protein will be precipitated. It is also thrown out by saturation 
of sodium chlorid or magnesium sulphate. Globulin is coagu- 
lated by heat at practically the same temperature as serum- 
albumin; i.e., 75 C. 



280 PHYSIOLOGICAL CHEMISTRY 

Laboratory Exercise LXIV. 
Experiments with Albumin and Globulin. 

The albumins and globulins respond to all the general re- 
actions of Laboratory Exercise No. 63. 

Exp. 163. A specimen of solid egg-albumin, prepared by 
evaporating a solution to dryness at 40 C, is provided. Test 
its solubility in water, alcohol, acetic acid, KOH solution, and 
concentrated HC1. Report results. 

Perform the following additional experiments, using a dilute 
(1/50) solution of egg-albumin. 

Exp. 164. Nitric-acid Test. — Take 15 c.c. of the solution in 
a wine-glass, incline the glass, and allow 5 c.c. of concentrated 
HNO3 to run slowly down the side to form an under layer. 
What other proteins respond to this test ? 

Exp. 165. Picric-acid Test. — Take a portion of the albumin 
solution and add a few drops of a solution of picric acid acidified 
with citric acid (Esbach's reagent). What other proteins re- 
spond to this test? 

Exp. 166. Action of {NH^iSO^. — To 10 c.c. of the albumin 
solution in a test-tube add some solid (NH 4 ) 2 S0 4 , shaking 
until solution is thoroughly saturated. Allow to stand a little 
while, shaking occasionally, then filter, saving the filtrate to test 
for albumin by the heat test. Report result. Test the solu- 
bility of the precipitate on the filter-paper. 

Exp. 167. Action of MgSO±. — Perform an experiment 
similar to Exp. 166 using solid MgS0 4 instead of (NH 4 ) 2 S0 4 . 
With what results ? 

Exp. 168. Salts of the Heavy Metals. — Note the action of 
the following: AgN0 3 , HgCl 2 , CuS0 4 , Pb(C 2 H 3 2 )2. Use solu- 
tions of the salts and of albumin. 

Why is white of egg an antidote in cases of metallic poison- 
ing? 



PROTEINS 281 



Globulins. 



The following tests serve to distinguish the globulins from 
other proteins. 

The tests may be made upon blood serum, or upon a globulin 
(edestin) which may be separated from hemp seed according to 
the following experiment: 

Extract about 1 ounce of crushed hemp seed with water 
containing about 5% sodium chlorid. This extraction should 
take from one-half hour to one hour at a temperature of about 
6o° C. Filter while hot. Upon cooling, a portion of the globu- 
lin (edestin) will probably separate out. Use the clear separated, 
fluid for the general protein reactions and precipitates. Boil 
the cloudy portion until the precipitated globulin has dissolved. 
Then set aside for 24 hours that the edestin may crystallize 
slowly, when hexagonal plates should be obtained. Examine 
by the microscope. (See Plate VII, Fig. 1, page 296.) 

Exp. 169. Action of C0 2 . — To 5 c.c. of blood serum add 
45 c.c. of ice-cold water. Place the mixture in a large test-tube 
or cylinder, surround it with ice-water, and pass through it a 
stream of C0 2 . A flocculent precipitate (paraglobulin) * will be 
formed. 

Exp. 170. Precipitation by Dialysis. — Into a parchment 
dialyzing-tube, previously soaked in distilled water, pour 20 c.c. 
of serum, swing the tube, with its contents, into a large vessel 
of distilled water, which is to be changed at intervals. Let 
stand twenty-four hours, then examine the serum in the dialyz- 
ing-tube; it will contain a flocculent precipitate of paraglobu- 
lin. Give explanation of cause of precipitation. 

Exp. 171. Pour a solution of globulin, drop by drop, into a 
large volume of distilled water (in a beaker). What takes 
place ? Explain. 

* Paraglobulin is a name applied to the globulin separated from blood serum. 



282 PHYSIOLOGICAL CHEMISTRY 

Exp. 172. Precipitation by Magnesium Sulphate. — Saturate 
about 5 c.c. of globulin solution with solid magnesium sulphate. 
A heavy precipitate will be formed. Compare this with the 
action of the same salt on the egg-albumin solution. Paraglo- 
bulin is so completely precipitated by this salt that the method 
is used for its quantitative estimation. 

The glutelins and prolamins thus far studied have been 
mostly obtained from vegetable sources. 

Glutenin constitutes about one-half of wheat gluten, and 
the prolamins mentioned on page 274; Zein is obtained from 
maize — Hordein from barley, Gliadin from wheat or rye and 
Bynin from malt. 

Albuminoids. 

Albuminoids are the simple protiens characterized by pro- 
nounced insolubility in all neutral salivas, and the common exam- 
ples are Keratin, from nails and hoofs, etc. ; Collagen, from bone 
and connective tissue; and Elastin, from tendons and ligaments. 

The differences in these substances are slight, the keratin 
being less soluble and less easily acted upon by digestive ferments 
than either of the other two. Keratin also contains more sul- 
phur. It is the principal constituent of horn, nails, hair, 
feathers, egg membrane, and some shells, such as turtle and 
tortoise. The sulphur content of these various sources differs 
considerably, ranging from about 5% in hair, about 3% in nail 
and horn, to 1.4% in egg membrane. 

The keratins are characterized by the fact that the sulphur 
which they contain is loosely combined; i.e., easily separated by 
the formation of hydrogen sulphide and other sulphur com- 
pounds as proved by experiment No. 174. The keratins are 
insoluble in dilute acids and unaffected by any of the diges- 
tive ferments; they do, however, dissolve in the caustic alkali 
solutions, and may be used as the source of leucin, tyrosin, 
cystin, and other well-known products of protein digestion. 






PROTEINS 283 

Collagen, upon hydrolization with boiling water, produces 
gelatin, which is a characteristic property of this class of pro- 
teins. It may be dissolved by both the gastric and pancreatic 
juices, especially if previously treated with warm acidulated 
water. 

Elastin contains the least sulphur of either of the three sub- 
stances which we have considered. It may be obtained from 
the ligamentum nuchae of an ox by chopping the ligament 
finely and extracting for two or three days with half saturated 
solution of calcium hydroxid. Like collagen it is dissolved upon 
prolonged treatment with proteolytic ferments. 

Bone. 

If all organic matter is burned off from bone, there remains 
the bone-earth, so called, made up of the phosphates and car- 
bonates of lime and magnesia, with slight amounts of chlorin, 
fluorin, and of sulphates, the proportion being practically the 
same as given for dentine, under Teeth, on page 178. Because 
in some diseases, in which the bones are softened or decalcified 
(as osteomalacia), the relation of the CaO and P 2 5 remains 
unchanged, it has been claimed that these substances exist in 
the bone in the form of a definite phosphate-carbonate contain- 
ing three molecules of the tribasic phosphate to one of carbon- 
ate: 3 Ca 3 (P0 4 )2.CaC0 3 . 

If, by treatment with dilute hydrochloric acid, the min- 
eral constituents are entirely dissolved out of bone, there re- 
mains a substance from which glue (gelatin) is derived, of 
similar composition to collagen, from connective tissue, and 
known as ossein. Neither of these (ossein or collagen) is sol- 
uble in water or in dilute acids. 

Gelatin is made by hydrolysis of ossein or collagen brought 
about by prolonged boiling with dilute mineral acids. Gelatin, 
if first treated with cold water till soft, may be dissolved in hot 



284 PHYSIOLOGICAL CHEMISTRY 

water. The solution is precipitated by mercuric chloric!, alcohol, 
tannic, and picric acids. It responds but feebly to the general 
protein reactions, but, by digestion with either pepsin or trypsin, 
compounds are obtained analogous to those resulting from 
similar protein digestion. 

Laboratory Exercise LXV. 
Experiments with Keratin and Gelatin. 

Keratins are characterized by their insolubility, and by their 
high content of loosely combined sulphur. 

Exp. 173. Test solubility of keratin (nail or horn) in water, 
acids, alkalies, gastric and pancreatic juices. 

Exp. 174. Warm a bit of keratin with 5 c.c. strong NaOH 
solution for a few minutes, and add a few drops of a lead acetate 
solution. What is the result ? 

Exp. 175. Gelatin. — Take about 10 grams of bone, prefer- 
ably small pieces of the shaft of a long bone, clean carefully, 
and allow to stand for a few days in 60 c.c. of dilute HC1 (1/20). 
The dilute acid dissolves the inorganic portion of the bone, 
leaving the collagen. Note the effervescence due to the pres- 
ence of carbonates. The acid solution is poured off and kept 
for further investigation. The remains of the bone are allowed 
to stand over night in a dilute solution (1/10) of Na 2 C0 3 , and 
then boiled in 100 c.c. of water for an hour or two. The col- 
lagen undergoes hydration and is converted into gelatin, which 
dissolves. A core of bone untouched by the acid usually re- 
mains. Evaporate the solution to 25 c.c. bulk and allow to 
cool. A firm jelly is formed if the solution is sufficiently con- 
centrated. If the solution gelatinizes, add an equal bulk of 
water and heat anew. With the solution perform the following 
experiments. (If too little gelatin is obtained for all the tests, a 
solution will be provided.) 

Gelatin may also be prepared from tendons which consist 



PROTEINS 285 

almost wholly of white fibers. Collagen is the substance of 
which white fibers are made up. 

Exp. 176. With a solution of gelatin make the usual tests 
for protein. 

Exp. 177. Precipitate gelatin from dilute solution with the 
following reagents: 

(a) Tannic acid. 

(b) Alcohol. 

(c) Acetic acid and potassium ferrocyanid. 

(d) Mercuric chlorid. 

(e) Picric acid. 

Conjugated Proteins. 

These are substances which contain the protein molecule 
united to some other molecule or molecules otherwise than as a 
salt. The conjugated proteins which we shall study are mucin, 
a type of glyco-protein, yielding upon decomposition a sub- 
stance containing a carbohydrate group; caseinogen (from milk), 
a phosphorus containing substance; and hemoglobin (from 
blood). 

The glyco-protein. Mucin, a selected type of this class of 
protein substance, occurs in various forms in saliva, in urine, bile, 
and other body fluids. The mucin substances are differentiated 
from the true mucins, according to Hammarsten, by the fact that 
the latter form mucilaginous or ropy solutions by the aid of a 
trace of alkali, from which they are precipitated by acetic acid. 
The precipitate is insoluble in excess of acid, or soluble only 
with great difficulty. 

True mucins have been separated and examined from the 
secretion of the submaxillary glands, from snails, from mucous 
membranes of the air passages, from synovial fluid, and from the 
navel cord. 

Mucin is quite readily converted to metaprotein by boiling 
with dilute acid, and, by action of strong acid, will yield a 



286 PHYSIOLOGICAL CHEMISTRY 

number of the simpler amino acids. Mucin itself is acid in re- 
action, but there is no evidence that it has power to form salts. 

The mucins are insoluble in pure water, but dissolve upon 
the addition of traces of alkali. The solution thus obtained will 
give the usual color reactions for the proteins. 

The action of mucin as a factor in dental caries, formation of 
gelatinous plaques, etc., will be discussed under Saliva. 

Caseinogen, the second conjugated protein which we shall 
consider, is the principal nitrogenous constituent of milk and 
will be studied as such. 

Milk. 

Milk is the characteristic secretion of mammals and con- 
tains the three great classes of food material, viz. : the proteins, 
carbohydrates and fats. The fat is held as a permanent emul- 
sion in so-called milk plasma. 

The plasma consists of water holding in solution caseinogen, 
albumin with a trace of globulin, milk sugar (lactose) and mineral 
salts. 

Specific Gravity. — Milk contains two different sorts of sub- 
stances influencing the gravity; first, the fat being lighter than 
the water tends to decrease the gravity; second, the solids not 
fat which are heavier than water tend to increase the gravity of 
the milk. Consequently, it may happen that a very poor milk 
and a very rich milk will have the same specific gravity; e.g., the 
normal gravity of whole milk is about 1.031, while the gravity 
of skim milk will be about 1.035 or 1.036, and that in which cream 
occurs in large amount may be as low as 1.015 or 1.020. It can 
be easily seen that starting with whole milk, the addition of 
cream or the addition of water will both alike reduce the gravity. 
Hence, taken alone, the gravity tells little or nothing as regards 
the quality of milk; but, if the gravity is taken together with 
the fat content, the two factors give oftentimes sufficient infor- 
mation. 



PROTEINS 287 

The relation between the gravity of the fat and the total 
solids is approximately constant, and the following formula 
will give the amount of total solids usually within 0.10 or 0.15 
of 1%. 

Total solids = ^t^- 6 + 5p^: + 0.46. 
5 4 

Reaction. — The reaction of cow's milk, when perfectly 
fresh, is amphoteric to litmus; i.e., it will both redden blue litmus 
paper and turn red litmus blue at the same time. This double 
reaction is due to the presence of various salts, probably the 
acid and alkaline phosphates. 

Cow's milk is acid to phenolphthalein, and this acidity 
naturally increases by the multiplication of various acid-forming 
bacteria, which produce lactic acid by hydrolysis of the milk 
sugar. When the acid strength has increased sufficiently, the 
caseinogen is decomposed, and casein is produced and pre- 
cipitated. 

This casein constitutes the curd, and the process, is the 
ordinary souring of milk. 

Lactic acid is not the only acid produced in the spontaneous 
fermentation of milk, as traces of formic, acetic, butyric and 
succinic acids have been demonstrated by different investiga- 
tors. 

The degree of acidity of milk is conveniently determined as 
suggested by W. Thorner (Chem. Zeit, 1891, page 1108, abst. 
analyst XVI, 200), 10 c.c. of milk with an equal volume of water 
and a few drops of phenolphthalein as indicator are titrated with 
N/10 alkali and every tenth of a degree of alkali used is con- 
sidered as representing one " degree " of acidity. 

By experimenting on samples kept under various con- 
ditions, Thorner found that milk coagulates on boiling when 
the acidity reaches 23 . Adopting 20 as the permissible limit 
of acidity, he proposes the following test: 10 c.c. of milk, 20 c.c. 



288 PHYSIOLOGICAL CHEMISTRY 

of water, a few drops of indicator and 2 c.c. of decinormal 
alkali are thoroughly mixed; if any red color, however weak, 
results, the milk will not coagulate upon boiling.* 

This method is given partly for its own sake and partly be- 
cause exactly the same method is used by Dr. Eugene S. Talbot 
of Chicago and many others for the determination of acidity of 
urine. By slight modification it may be used for saliva. The 
record of slight amounts of acidity made in degrees in this way 
has several practical points in its favor. 

Casein is the principal protein found in milk. It exists in 
combination with calcium salts as caseinogen. This combina- 
tion is broken up and the casein precipitated by the action of 
rennin and other enzymes, by acids, and by certain inorganic 
salts. 

Casein is classified as a pseudo-nucleo-albumin. The nucleo- 
proteins, so named because true nuclein may be obtained from 
them, are constituents of the cell nuclei, and differ in composi- 
tion from ordinary proteins by containing from 0.5 to 1.6% of 
phosphorus. Casein from cow's milk contains, according to 
Hammarsten, 0.85% of phosphorus. It has been classified as 
a ^se^0-nucleo-albumin because, upon digestion with pepsin, 
pseudo-nuclein rather than true nuclein is obtained. 

Casein is practically insoluble in water, but dissolves readily 
in dilute alkaline solutions. Its precipitation as curd is de- 
pendent upon the presence of calcium salts. 

Lactalbumin is the only other protein substance worthy of 
note in milk. This may be found in the filtrate after separat- 
ing the casein. The total proteins contained in human milk 
average from 1.5 to 2.5 per cent, while in cow's milk the proteins 
are 3.0 to 4.5 per cent. This difference, together with the vari- 
ation of reaction and sugar-content, makes it necessary to 
" modify" cow's milk when it is used as an infant food. 

The modification usually consists in the addition of lime- 

* From Allen's Commercial Organic Analysis, Vol. 4. 



PROTEINS 



289 



water (to change the reaction), of water (to reduce percentage of 
proteins), and of cream and milk-sugar (to increase fat and 
lactose). 

The following table shows comparative composition: 





Reaction. 


Total 
Solids. 


Proteins. 


Sugar. 


Fat. 


Ash. 


Human milk . . 
Cow's milk. . . 


Alkaline 
Acid 


13.00% 
14.00% 


2.70% 
4.15% 


6.10% 
4-90% 


4.00% 
4.25% 


0.20% 
0.70% 



Fat. — The fat of milk exists as microscopic globules appar- 
ently inclosed in a protein-like membrane separating substance, 
the presence of which seems a necessary theory to account for 
the behavior of milk fat toward various solvents such as ether. 
The milk fat or butter fat consists largely of olein and palmitin 
with a slight amount of butyrin and traces of several other fatty 
acids. 

Milk, as has already been stated, undergoes lactic acid 
fermentation readily and this may be induced by a considerable 
number of microorganisms. It is 
not, however, liable to alcoholic 
fermentation except under peculiar 
circumstances. Alcoholic fermen- 
tation may be induced by certain 
ferments, such as the Kephir grain 
used quite largely in the East, the 
product being known as Kumiss 
or milk wine. Kumiss originally 
was produced from mare's milk, 
but the name has also been applied 
to any milk which has undergone alcoholic fermentation. 

Colostrum is a peculiar substance occurring at the very 
earliest stages of lactation. Its specific gravity is considerably 
higher than that of milk, being 1.040 to 1.060. It contains 




Fig. 18. Milk and Colostrum. 



290 PHYSIOLOGICAL CHEMISTRY 

much more protein substance and is characterized by the pres- 
ence of granular corpuscles known as colostrum corpuscles. 
(Fig. 1 8, on page 289.) 

Laboratory Exercise LXVI. 

Experiments with Mucin and Milk. 

Exp. 178. Examine microscopically whole milk 2 skim-milk, 
and cream. Note the relative amounts of fat in the three 
varieties. 

Exp. 179. Shake a little cream with chloroform in a test- 
tube; separate the chloroform, evaporate, and melt the fat 
residue obtained; allow it to cool slowly, when fat crystals will 
be obtained, which may be examined under the microscope and 
micropolariscope. 

Exp. 180. With a lactometer take the specific gravity of 
whole milk and skim-milk and explain the difference in results. 

Exp. 181. Test the reaction of milk with litmus. 

Exp. 182. Dilute some milk with six or seven times its 
volume of water, and add acetic acid drop by drop till the 
casein is precipitated. Filter and reserve the precipitate. Test 
the nitrate for proteins, if any remain; determine if possible 
their character. 

Exp. 183. Test another portion of the nitrate for carbohy- 
drates, determining the variety present. 

Exp. 184. To 50 c.c. of milk add a few drops of rennin 
solution; keep at a temperature of 40 C. for a few minutes, 
and explain results. 

Exp. 185. Take a portion of the precipitated casein from 
Exp. 182, digest at 40 C. with pepsin HC1 for twenty minutes 
or half an hour. While digesting, test other portions of casein, 
for solubility in water, in dilute acid and dilute alkali. Test 
also a portion for phosphorus by boiling in a test-tube with 
dilute nitric acid, cooling to at least 50 C, and adding ammo- 
nium molybdate solution. 



PROTEINS 291 

Exp. 186. To a little skim-milk contained in a test-tube add 
a saturated solution of ammonium sulphate. 

Exp. 187. To a solution of mucin* found on the side shelf 
add acetic acid till precipitation takes place. Settle, filter, 
wash, and test solubility in water, dilute alkali solution and 
5% HC1. 

Exp. 188. Make color- tests for proteins. 

Exp. 189. Boil a little mucin solution with dilute HC1 for 
several minutes. Cool, neutralize, and test for sugar. 

Derived Proteins. 

Meta-proteins — Acid Meta-protein. — The digestive action 
of the gastric juice on protein substances is the formation of an 
acid meta-protein, formerly called acid albuminate. The meta- 
proteins are characterized by the fact that they are precipitated 
on neutralization and are not coagulated by heat. They may 
also be precipitated by saturation with common salt. 

The Alkali Meta-protein or alkali albuminate is the stronger 
of these two classes of compounds when considered from a chem- 
ical standpoint; that is, the reactions are more marked, and some 
compounds will be formed with the alkali albuminate which are 
not produced when the acid albuminate is treated in a similar 
way. The acid meta-protein from the digestion of meat is known 
as syntonin. 

The Proteoses (albumoses) may be considered as the next 
well-defined protein product of protein digestion following the 
albuminate. That is, leaving out the many intermediate prod- 
ucts between which sharp lines of demarkation cannot be 
drawn, the decomposition of albumin brought about by enzymes 
or digestive ferments gives, first, acid albumin; second, albumose; 
and third, peptone. Albumose may be taken as a type of this 
second class of digestive products. Other proteoses, such as 
globulose, etc., are the substances derived from other proteins 

* For preparation of mucin solution from navel cord, see Appendix. 



292 PHYSIOLOGICAL CHEMISTRY 

at a corresponding point of decomposition or peptic digestion. 
Albumose may be coagulated by heat at a temperature ranging 
upwards from 56 C, but, unlike albumin, as the temperature 
approaches the boiling-point the albumose goes again into solu- 
tion, and at a boiling temperature may be separated from albumin 
by nitration. As the filtrate cools, albumose will again precipi- 
tate. The albumose is also precipitated by nitric acid, by ferro- 
cyanid of potassium and acetic acid (the precipitate in both cases 
being dissolved by heat), and the other general protein precipi- 
tates. The biuret test gives a distinctive color with proteoses 
and peptones, it being a marked reddish shade rather than the 
violet or blue obtained with other proteins. 

Peptones are the final products of peptic digestion of the 
proteins. They are soluble substances which give the biuret 
test similarly to the proteoses, but are not precipitated by heat, 
by nitric acid, by potassium ferrocyanid and acetic acid, nor 
by saturation with ammonium sulphate. 

Peptids. — The peptids are the simpler forms of the pep- 
tones, many of them being complex amino acids. Upon decom- 
position or hydrolytic splitting of peptid, the simpler amino acid, 
which is without the protein characteristics, results. 

Laboratory Exercise LXVII. 
Experiments with Protein Derivatives. 

Preparation of Metaprotein. To a solution of egg-albumin 
add a few drops of a 0.5% solution of NaOH, and warm gently 
for a few minutes. With the solution thus obtained perform 
the following tests : 

Exp. 190. (a) Effect of Heating. — Boil some of the solution 
and report result. 

Exp. 191. (b) Effect of Neutralizing. — Add a drop of 
litmus solution, and cautiously neutralize. 



PROTEINS 293 

Acid Metaprotein. 

Exp. 192. Add a small quantity of a 0.2% HC1 solution to a 
solution of egg-albumin, and warm at 40 C. for one half to one 
hour. Or cover with an excess of 0.2% HC1 some meat cut 
into fine pieces, and expose for a while to a temperature of 
40 C. Filter. With either of the solutions thus obtained 
make same tests as on alkali metaprotein, and compare results. 
How distinguish between them? 

Albumoses (Hemialbumose). — This name includes four 
closely allied forms of albumose, namely: (1) Protoalbumose ; 
(2) Deuteroalbumose; (3) Heteroalbumose ; (4) Dysalbumose, 
an insoluble modification of heteroalbumose. Commercial 
peptone, which is substantially a mixture of albumoses and pep- 
tones, will be given out for use. 

Exp. 193. Make a solution of the peptone in water, filter 
if necessary, and saturate with solid (MH^SO^ Filter. The 
precipitate contains the albumoses, the filtrate the peptones. 
Reserve the filtrate for subsequent tests for peptone. Wash the 
precipitate with a saturated solution of ammonium sulphate; 
dissolve in water, and, with the solution obtained, perform the 
following tests, noting especially the tendency of albumose pre- 
cipitates to dissolve upon the application of heat and to reappear 
upon cooling. 

Using this solution of albumose, repeat Exps. 155, 156, 157, 
164, 165. If no precipitate forms with HN0 3 in Exp. 164, add 
a drop or two of a saturated solution of common salt. (Deutero- 
albumose gives this reaction only in the presence of HC1.) 

Exp. 194. Saturate some of the solution with (NH 4 ) 2 S0 4 . 
Report the result. 

Exp. 195. To some of the solution add 2 or 3 drops of acetic 
acid and then a saturated solution of NaCl. A precipitate 
forms, which dissolves on heating, and reappears on cooling. 

Exp. 196. Using the peptone solution prepared in manner 



2 94 PHYSIOLOGICAL CHEMISTRY 

above described from commercial peptone, repeat the experi- 
ments indicated in Exp. 193. 

Exp. 197. Effect of heating. — Boil some of the peptone solu- 
tion. Report the result. 

Exp. 198. Power of Dialyzing. — Dialyze some of the pep- 
tone solution. Use 10 c.c. of the peptone solution, and in the 
outside vessel about 100 c.c. of water, which in this case is not 
to be changed. After twenty-four hours test the outside water 
for peptone, employing the biuret test. 

Exp. 199. Action of Ammonium Sulphate. — Saturate some 
of the peptone solution with solid (NH 4 ) 2 S0 4 . Report the 
result. 

A number of unknown solutions will be given out to be 
tested for carbohydrates and proteins. A report of the results, 
together with the methods employed, is to be made. 



BLOOD AND MUSCLE. 

Blood. 

The blood, carrying oxygen and other forms of nutrition to 
all parts of the body, and returning carbon monoxid and the 
waste products of cellular activity, is an exceedingly complex 
substance. The composition of the blood itself, however, may 
be grossly described as a fluid (plasma) carrying in suspension 
the cellular constituents, red and white corpuscles. The plasma 
contains solid matter to the extent of about 8.9%. This is 
largely protein, consisting of serum globulin, serum albumin, 
a slight amount of nucleoprotein, and fibrinogen; also a fibrin 
ferment, thrombase or thrombin, by the action of which the 
fibrin is separated as a "clot" which mechanically carries down 
the corpuscles. As the clot contracts, the "serum" separates 
as a clear, amber-colored liquid, consisting of serum globulin 
(paraglobulin), serum albumin, and the fibrin ferment. 



BLOOD AND MUSCLE 295 

Fibrin. — The fibrin may be obtained free from corpuscles 
by whipping fresh blood. Under this treatment the fibrin 
separates as shreds, while the remaining fluid constitutes 
"defibrinated blood." The presence of lime-salts is essential 
to the coagulation of the blood, i.e., the decomposition of fibrin- 
ogen and separation of fibrin, in much the same way as in the de- 
composition of caseinogen and precipitation of casein from milk. 

Fibrin, as usually obtained, is in the form of brown, stringy, 
and " fibrinous" masses, which are kept under glycerin for labor- 
atory use. It is insoluble in water or alcohol. In dilute acid 
(HC1) or alkali solutions, it swells and ultimately dissolves, 
although it may be several days before solution is effected. The 
fibrins from the blood of different animals differ in composition, 
as indicated by marked differences in solubility. 

The chemistry of the red and white corpuscles is more complex 
and not so well known as the chemistry of the plasma, which 
we have considered. The red corpuscles consist of a frame of 
protoplasm, also called stroma, which contains lecithin, choles- 
trin, nucleoalbumin, and a globulin. (Hammarsten.) Upon 
and all through the stroma is the haemoglobin, which, together 
with its oxygen compound oxyhemoglobin, is responsible for 
the color of the blood. Oxyhemoglobin may be obtained as 
silky, transparent crystals of blood-red color. 

From haemoglobin may be derived the blood pigment hcenio- 
chromogen, containing iron, and this by oxidation is converted 
into haematin. The iron from the blood may, by decomposi- 
tion of the pigment and subsequent combination with sulphur 
(FeS), cause discoloration of teeth. This is the theory of 
Dr. Kirk of Philadelphia, and in the author's opinion is per- 
fectly sound, and far more probable than other explanations 
which have been offered, but which do not recognize the forma- 
tion of a sulphur compound. 

CO Haemoglobin. — Haemoglobin forms with carbon monoxid 
(from water-gas or other sources) a definite and very stable 



296 PHYSIOLOGICAL CHEMISTRY 

compound, being even stronger than the oxyhemoglobin, to 
which reference has previously been made. Blood containing 
carbon monoxid haemoglobin is of a bright-red color, which 
darkens in the air much more slowly than ordinary blood. 

Haemin, or Teichmann's haemin crystals, is the hydrochloric 
acid compound of haematin. (See Exp. 206, page 299, also 
Plate VII, Fig. 2.) 

The form of the red corpuscle is that of a biconcave disk 
without nucleus; by action of water it becomes swollen, and 
the haemoglobin may be washed away, leaving the " stroma." 
The diameter of the red corpuscles of human blood is about 
1/3200 of an inch. Of the domestic animals, the corpuscles of 
the dog approach most nearly to the measurement of the human. 
The sheep, horse, and ox have smaller corpuscles than man, 
while those of birds, cold-blooded animals, and reptiles are 
larger (see Plate VII, Figs. 5 and 6). 

The white corpuscles are rather larger than the red, and 
occur in much smaller numbers, a cubic millimeter containing 
about 5,000,000 red to 7500 white. The white corpuscles pre- 
sent a much greater diversity of character than do the red. 
They contain one to four nuclei, and are capable of amoeboid 
movements. The white corpuscles are also called leucocytes, 
aggregations of which constitute pus. The leucocytes are di- 
vided histologically into various classes, — lymphocyte, neutro- 
philes, eosinophiles, etc., — according as they are acted upon 
by different staining-nuids or fulfill some particular office; but 
these are not to be distinguished chemically. 

Muscle. 

The chemistry of muscle is complex. It changes rapidly 
upon the death of the animal, so much so that the liquid which 
may be expressed from living muscle (or from muscle frozen 
immediately upon the death of the animal) has been called 
muscle plasma, in distinction from the fluid obtained in the 



PLATE VII.— PHYSIOLOGICAL CHEMISTRY. 




Fig. i. 
Edesten. 




Fig. 3.— Fat Crystals. 
A, Butter Crystals; B, Lard Crystals 




Fig. 5. 

A, Human Blood; B, Horse Blood; 

C, Dog Blood. 




Fig. 2. 
Teichmann's Hemin Crystals. 




Fig. 4. 
A, Fat Acid; B, Cholesterin. 




Fig. 6. 
A, Frog Blood; B, Chicken Blood; 
C, Fish Blood. 



BLOOD AND MUSCLE 297 

same manner from dead muscle, which is called muscle serum. 
The chemical reactions of these solutions differ, due to the 
formation of sarcolactic acid in the dead muscle. The proteins 
differ in certain respects. Myosin is the most essential con- 
stituent of muscle plasma, and corresponds to the fibrin of the 
blood-clot. It exists as a parent protein myosinogen, or 
myogen, from which it may be precipitated by saturation with 
salt or magnesium sulphate. Myosin has many of the prop- 
erties of the globulins, but differs in the very important particu- 
lar of not being precipitated by dialyzation. Among the more 
important extractive bodies obtained from muscle are creatin, 
carnin, inosite, glycogen, and lactic acid. Creatin is a xanthin 
body, being chemically a methyl-guanidin-acetic acid, which 
may appear in the urine as creatinin. (Creatinin is creatin 
minus H 2 0.) 

Carnin is a white crystalline substance obtained from meat 
extract and converted by oxidation induced or produced by 
nitric acid, chlorin or bromin into hypoxanthin or sarkin. Its 
chemical constitution is not positively known. 

Inosite, C 6 Hi206+H 2 0, is a hexahydroxybenzene, C 6 H 6 (OH) 6 
+ H 2 0. It has a sweet taste, and was formerly erroneously 
classed with the carbohydrates. It is capable of yielding lactic 
and butyric acids ( ?) . 

Glycogen occurs in slight amounts in muscle, but decomposes 
after death, with formation of a reducing sugar. (Compare 
page 264.) 

Lactic Acid is a constituent not only of muscle but also of 
various glands, of the bile, and of blood. For the chemistry 
of this substance, see page 220. 



298 PHYSIOLOGICAL CHEMISTRY 

Laboratory Exercise LXVIII. 
Experiments on Blood. 
Exp. 200. Test the reaction of blood with a piece of litmus- 
paper which has been previously soaked in a concentrated NaCl 
solution. To what is reaction due? 

Exp. 201. Blood-corpuscles. — (a) Examine a drop of blood 
under the microscope. Sketch the red and white corpuscles. 

(b) Note the difference between the corpuscles of mammals 
and those of birds and reptiles. 

(c) Note the effect upon the red corpuscles produced by the 
addition of (1) water, (2) a concentrated solution of salt. 

Exp. 202. Hcemoglobin Crystals. — Place a drop of de- 
fibrinated rat's blood on a slide; add a drop or two of water; 
mix, and cover with a cover-glass. Sketch the crystals which 
separate after a few minutes. Or instead of above add a few 
drops of ether to some blood in a test-tube; shake thoroughly 
until the blood becomes "laky," and then place the tube on 
ice till crystals appear. 

Exp. 203. A spectroscope will be found ready for use in the 
laboratory, and the absorption-bands given by oxyhemoglobin 
and haemoglobin will be demonstrated. The student may pre- 
pare solutions for examination as follows: 

(a) Oxyhemoglobin. — Use dilute blood (one part of de- 
fibrinated blood in fifty parts of distilled water). 

(b) Hcemoglobin (reduced haemoglobin) . — Add to blood a few 
drops of strong ammonium sulphid, or one or two drops of 
freshly prepared Stokes's reagent.* Note the change in color 
produced by the addition of the reducing agent. Shake with air 
and note the rapid change to oxyhaemoglobin. 

(c) Hcemochromogen. — To a little of the haemochromogen, 
reduced with ammonium sulphid, add a few drops of concen- 

* Stokes's reagent consists of two parts of ferrous sulphate and three parts of 
tartaric acid dissolved in water and ammonia added to distinct alkaline reaction. 
There should be no permanent precipitate. 



BLOOD AND MUSCLE 299 

trated NaCl, and note the spectrum of reduced haematin or 
haemochromogen . 

(d) Carbonmonoxid Hcemoglobin. — Pass a current of illumin- 
ating gas through a dilute oxyhemoglobin solution for a few 
minutes and filter. Note the change of color. Try the effect on 
the solution of (1) ammonium sulphid; (2) Stokes's reagent; 
(3) shaking with air. Note the stability of the compound. 

Exp. 204. Take the specific gravity of blood by filling a test- 
tube one-half full of benzene; add one drop of blood, and then 
add chloroform, a drop at a time, with careful but thorough mix- 
ing, until the drop of blood floats at about the middle of the 
mixture, indicating that the gravity of the mixture and of the 
blood are the same. The specific gravity of the benzene and 
chloroform may be taken in any convenient way. 

Exp. 205. Make the guaiacum test for blood on a sample of 
dried blood; also on potato scrapings. The method is as follows: 

To a little clear solution of blood or material obtained from 
potato scrapings, add some fresh tincture of guaiacum ; then add 
a few drops of an ethereal solution of hydrogen peroxid, shake 
the mixture and note the blue color obtained. 

From these two tests what do you gather about the value of 
the guaiacum test for blood, and what is probably the cause of 
the coloration? 

Exp. 206. Hcemin Crystals (Teichmanri's Test). — Place a 
bit of powdered dried blood on a glass slide; add a minute 
crystal of NaCl (fresh blood contains sufficient NaCl) and two 
drops of glacial acetic acid. Cover with a cover-glass and warm 
gently over a flame until bubbles appear. On cooling, dark- 
brown rhombic crystals, often crossed, separate (chlorid of 
haematin). Similar crystals can be obtained by using an alka- 
lin iodid or bromid in place of NaCl. 

Exp. 207. Coagulation of Blood. — Observe the phenomena 
of coagulation as it takes place (a) in a test-tube; (6) in a 
drop of blood examined under the microscope. Explain fully. 



300 PHYSIOLOGICAL CHEMISTRY 

Exp. 208. Proteins of Blood-plasma. — (a) Serum-albumin. 
(b) Serum-globulin. Using blood-serum, separate and identify 
these two proteins. 

(c) Fibrinogen. — Fibrinogen is a globulin found in blood- 
plasma, lymph, etc., together with paraglobulin. Like para- 
globulin it responds to all the general precipitants and tests, and 
in addition gives the reactions with C0 2 , dialysis and MgS0 4 . 
It is distinguished from paraglobulin easily by two reactions, viz., 
its power to coagulate, i.e., to form fibrin when acted on by fibrin 
ferment, and its temperature of heat coagulation, which will be 
found to be from 5 6° to 6o° C. 

Exp. 209. Fibrin. — (a) Note its physical properties. 

(b) Note action of 0.2% hydrochloric acid. 

(c) Apply the protein color tests. 

Laboratory Exercise LXIX. 
Experiments with Muscle. 
Exp. 210. Place 25 grams of fresh finely chopped muscle 
in a beaker with 75 c.c. of 5% solution of common salt, and 
allow to stand for about one hour, with frequent stirring. (In 
the meanwhile perform Exp. 211.) Then filter off the liquid 
and make the following tests with the filtrate : 

(a) Test for proteins. 

(b) Having found proteins, pour a little of the solution into 
a beaker of water. Result. Inference (myosin). 

(c) Make a fractional heat coagulation in the following man- 
ner (upon the care with which the temperatures given are ad- 
hered to, depends the success of the separation) : Warm to from 
44 to 50 C, and keep at that temperature for a few minutes. 
The coagulum is myosin [synonyms: paramyosinogen (Halli- 
burton), musculin (older authors)]. In solutions the myosin, 
which has the properties of a globulin, becomes insoluble after a 
time, because it changes to myosinfibrin. In heating the solu- 
tion as above, a slight cloud may appear at from 30 to 40 C. 



BLOOD AND MUSCLE 301 

This is due to coagulation of soluble myogenfibrin. Now filter 
off the coagulated myosin. 

Heat filtrate to from 55 to 65 C. The coagulum is myogen 
(synonym: myosinogen). In spontaneous coagulation of its 
solutions it forms, first, soluble myogenfibrin, and, finally, in- 
soluble myogenfibrin. Filter. 

Heat to from 70 to 90 C. Coagulum is serum albumin from 
the blood within the muscle, and is not a constituent of the muscle 
plasma. Filter. 

Test filtrate for proteins. If it shows a slight biuret test, 
this is due either to incomplete precipitation by coagulation 
or to the post-mortem formation of albumose or peptone by 
auto-digestion (autolysis) . 

Exp. 2ii. Make an aqueous extract of muscle, and test for 
lactic acid by acidulating with H 2 S0 4 , extracting with ether 
and testing the ethereal extract with very dilute ferric chlorid 
solution. The presence of lactic acid is shown by a bright- 
yellow color. 

Exp. 212. Creatin may be most conveniently prepared 
from a strong solution of Liebig's extract. Dissolve the extract 
in twenty parts of water, add basic lead acetate drop by drop to 
avoid more than a slight excess, then remove excess of lead; 
concentrate to a syrup over a water-bath and allow to stand in 
a cool place, when creatin crystals will separate out. Two or 
three days' time may be required before the crystals are ob- 
tained. They may be washed with 88% alcohol and purified 
by recrystallization from water. Hypoxanthin and sarcolactic 
acid may be obtained from the mother liquor.* 

Exp. 213. Creatinin may be prepared from creatin by 
boiling for ten or fifteen minutes with very dilute sulphuric acid. 
Neutralize the acid with BaC0 3 , filter, evaporate to dryness on 
a water-bath, and extract the creatinin with alcohol. Upon 
evaporation the creatinin is obtained in the form of crystals. 

* Lea's Chemical Basis of the Animal Body. 



PART VII 

DIGESTION. 



CHAPTER XXXIII. 

SALIVA PROPERTIES AND CONSTITUENTS. 

The saliva is a mixed secretion from the parotid, submax- 
illary, and sublingual glands, together with a slight amount 
obtained from the smaller buccal glands. The chemical com- 
position of the secretion from these various sources differs con- 
siderably, but from a chemical standpoint we are much more 
interested in the mixed saliva and its constituents than the 
differences in the product of the various glands. The notable 
differences are that the mucin is practically wanting in the 
parotid saliva. The alkaline salts seem to be in smaller pro- 
portion in the parotid saliva than in the other two. Potassium 
sulphocyanate is a constituent of all varieties of saliva, although 
more constantly present in the submaxillary and in the sublingual 
than in the parotid. The parotid, on the other hand, contains 
a larger proportion of dissolved gases. The data on the com- 
position of these varieties differ to a considerable extent and 
comparisons are not wholly satisfactory. 

The mixed saliva contains, according to Professor Michaels, 
all the salts of the blood which are dialyzable through the salivary 
glands, and hence furnishes a reliable index of metabolic proc- 
esses which are being carried on within the system. In order 
for this fact to be of practical values, two things are obviously 
of prime importance: First, methods of analysis which are not 
too complicated and at the same time conclusive; second, a 

302 



SALIVA PROPERTIES AND CONSTITUENTS 303 

knowledge regarding the source of the various constituents 
found which will enable us to make a rational interpretation of 
the results obtained. In both of these fundamentals we are very 
much hampered by lack of knowledge ; as yet there is much to be 
desired in the way of practical clinical tests for the various 
salivary constituents, and very much to be learned as to their 
meanings in order to make deductions which shall be conclusive. 
We are led to believe from the work of an increasing number of 
specialists that this subject of salivary analysis promises much 
and is certainly worthy of careful investigation. 

The quantity of saliva secreted in twenty-four hours is var- 
iously estimated from a few hundred to 1500 c.c; 1200 to 1500 
is the more probable amount. The quantity is diminished in 
fevers, severe diarrhoea, diabetes, and nephritis, by fear and 
anxiety, and by the use of atropine. It is increased by smoking, 
by mastication, by the use of mercury, potassium iodid, or 
pilocarpin. The flow of saliva is also increased by action of the 
sympathetic nervous system, during pregnancy, and by local 
inflammatory process. 

Physical Properties. — The physical properties of saliva in- 
clude its appearance, specific gravity, reaction, color, and odor. 

Appearance. — The appearance is clear, opalescent, frothy, 
or cloudy; normal saliva is usually opalescent. It may become 
turbid by precipitation of lime-salts caused by the escape of 
carbon dioxid. 

Specific Gravity. — Specific gravity ranges from 1.002 to 1.009, 
the total solids being only from 0.6 to 2.5 per cent. 

Reaction. — The reaction is normally alkaline to litmus- 
paper or to lacmoid. Normal saliva, however, fails to give 
an alkaline reaction with phenolphthalein, due to the presence 
of free C0 2 , which may be present to the extent of 19 parts in 
100, by volume. If the sample be subjected to even a slight 
degree of heat the acid gas is expelled; then the usual pink color 
may be obtained with this indicator. Saliva may be acid upon 



304 DIGESTION 

fasting, particularly before breakfast and also after much talk- 
ing. Acid conditions may exist which are local in their char- 
acter and due to lactic acid fermentation. Acid salivas may 
also be met with in cases of rheumatism, mercury salivation, 
and diabetes. By exercise of the glands, as during the chew- 
ing of food, the alkalinity is increased; oftentimes the reaction 
changes from faintly acid to alkaline during this process, the 
proportion of alkaline salts becoming greater, although the total 
solids as a whole are slightly diminished. This fact of the 
change in the reaction from acid to alkaline has been explained by 
ascribing the acidity due to fermenting particles in the mouth; 
the continued process of chewing and swallowing washes this 
away, or, in other words, the change in reaction is a mechan- 
ical one rather than a change of the chemical composition of the 
secretion. This explanation seems to be a superficial one and 
without sufficient experimental foundation. 

The acidity of saliva, as indicated at the opening of this 
paragraph, is referred to the behavior of the saliva to phenol- 
phthalein, and is in large part due to the presence of free carbon 
dioxid. 

The sources of C0 2 in saliva are probably three. C0 2 
dialyzed through the salivary glands, traces from carbohydrate 
fermentation, and considerable quantities absorbed from con- 
tact with expired air. 

The saliva obtained by chewing paraffin (a process calcu- 
lated to furnish the maximum amount from the last two sources), 
may yield several times the amount of free C0 2 that another 
sample taken from the same patient by a saliva ejector will give. 

Acidity of saliva may be temporary when it may be entirely 
removed by drawing air through the heated (not boiled) sample. 
The permanent acidity may be determined by titration of the 
sample after removal of C0 2 . 

The apparatus pictured in Fig. 19 has been used by the 
author for this acidity determination. 



SALIVA PROPERTIES AND CONSTITUENTS 



305 



The air is drawn from left to right first through a potash 
bulb (A) to absorb atmospheric C0 2 , next through 10 c.c. of 
saliva diluted with 20 c.c. of water contained in a small Soxhlet 




Fig. 19. 

flask (B) whereby the C0 2 from the saliva is carried through the 
" test-tube condenser" and collected in baryta water in the 
Erlenmeyer flask (C) at the left. This in turn is connected with 
a suction pump or aspirator. The "drip cup" (D) has been 
found necessary when working with very viscid samples. The 



306 DIGESTION 

thistle tube (E) holds water for maintaining the volume in (B) 
if the condenser is not used. 

The amount of free C0 2 may be determined by adding a stand- 
ard carbonate solution (N/ioo Na 2 C03) to a volume of baryta 
water equal to that used in the Erlenmeyer flask and then com- 
paring the degree of turbidity obtained. This may be done by 
viewing through flat-bottom tubes (shell tubes) of about 20 c.c. 
capacity, or, in many cases, better, by use of the Duboscq col- 
orimeter used for determination of ammonia (Fig. 20, page 307). 

Permanent acidity is of comparatively rare occurrence and 
is due either to the presence of acid salts, such as NaH 2 P0 4 , or 
slight amount of organic acids possibly combined as acid meta- 
protein. This acidity and its clinical significance is at present 
under investigation. 

Color. — Saliva is usually colorless when fresh, but upon 
standing for twenty-four hours may assume various tints, 
which are developed from constituents derived from bile. (Pro- 
fessor Michaels.) Saliva may be colored red or brown by the 
presence of blood or blood pigments, but in such cases the 
source of the color is usually local and easily discovered. 

Odor. — Normal saliva is practically odorless. In cases of 
pyorrhoea there is usually a peculiar fetid odor easily recognized. 
In other pathogenic conditions the odor may be slightly ammonia- 
cal, or occasionally resemble the odor of acetone or garlic. 

Constituents. — We should here distinguish carefully be- 
tween saliva proper and sputum. The constituents of sputum 
are derived from the air-passages rather than from the salivary 
glands, and are not at present under consideration. Among 
the normal constituents of saliva are included mucin, albumin, 
ptyalin, also oxydizing enzymes, ammonium salts, nitrites, 
potassium sulphocyanate, alkaline phosphates, and chlorids, with 
traces of carbonates; and, in the sediment, epithelium cells, 
occasional leucocytes, and fat globules. The abnormal con- 
stituents will include glycogen, urea, dextrin, rarely sugar, 



SALIVA PROPERTIES AND CONSTITUENTS 



307 



cholesterin, derivatives from bile, lecithin, xanthin bodies or 
alkaline urates, acetone, lactic acid, and crystalline elements 
resulting from insufficient oxidation or perverted glandular func- 
tion. These latter are recognizable by the micropolariscope. 








Fig. 20. — Colorimeter. 

Mercury and lead may also be found in saliva in cases of poison- 
ing by salts of these metals. 

Mucin. — The secretion from the parotid gland contains 
practically no mucin, but the sublingual saliva contains large 
amounts. Mucin is, according to Simon, the most important 



308 DIGESTION 

constituent of the saliva, not excepting ptyalin. The various 
glands contributing salivary mucin do not in all probability 
furnish just the same kind of protein; moreover, the mucin 
from different individuals seems to vary in composition and 
properties, some yielding more abundant acid decomposition 
products than others (see article by W. D. Miller, in Dental 
Cosmos for November, 1905), while, according to Professor 
Michaels, the mucin varies much in the same individual in 
health and disease. The changes in the characteristics of 
salivary mucin have been studied but little, and the investiga- 
tion of these changes, as indications of diathetic states, promises 
much. 

An excess of mucin in the saliva tends to an increase of 
bacterial growth, from the fact that it furnishes increased 
facilities for multiplication; it may also give rise to mucic acid, 
which, according to Dr. G. W. Cook of Chicago, is a probable 
factor in tooth erosion. (See Dental Review, May, 1906, page 
461.) 

Albumin. — Albumin is present in very small quantities, 
increased during mercurial ptyalism, usually in cases of pyor- 
rhoea, and, according to some authorities, in various albuminu- 
rias. It may be detected by usual methods after the separation 
of mucin. 

"According to Vulpian, the quantity of albumin is increased 
in the saliva of albuminurics of Bright's disease. The saliva 
of a patient with parenchymatous nephritis had mucin 0.253 
and albumin 0.182 per cent. The saliva of another patient, 
with albuminuria of cardiac origin, contained mucin 0.45 y 
albumin 0.145 per cent. In a healthy man there was found 
mucin 0.320, albumin 0.05 per cent. This fact has been con- 
firmed by Pouchet, who found these substances in greater quan- 
tities."* 

* Dr. Joseph P. Michaels. S. S. White's reprint of paper read before Inter- 
national Dental Congress, Paris, 1900. 



SALIVA PROPERTIES AND CONSTITUENTS 309 

Ptyalin. — Ptyalin is the principal ferment of the saliva ; it 
converts starch, by hydrolysis through the various dextrins 
(page 264), to maltose. The maltose in turn is converted into 
glucose by a second ferment, known as maltase, which exists 
in saliva in very small quantities. 

The activity of ptyalin is greatest at a temperature of 40 C. 
Very faintly acid saliva is the best media. Neutral and faintly 
alkaline salivas are next in order. 

The amylolytic power of a given sample of saliva may be 
determined by the action on dilute starch paste. In making 
comparative tests it is essential that the conditions under which 
the ptyalin is allowed to act should be exactly the same, especially 
as regards the temperature and duration of the process. A 
slight variation in the strength of the starch solution is of no 
consequence, as starch is supposed to be in excess. (See Exp. 
214 on page 327, also method on page 322.) 

Ammonium Salts. — Ammonium salts occur chiefly as chlorid, 
probably to some extent as sulphocyanate, and occasionally as 
oxalate. Professor Michaels says that ammonia must be con- 
sidered as a more completely oxidized form of nitrogen than urea ; 
hence its relative increase is observed in all diseases which occa- 
sion an excess of nitrogen and urea, as in tuberculosis and all 
hypoacid diatheses. There is a decrease of ammonia whenever 
the nitrogen fails to reach the stage of oxidation represented by 
urea. This condition is accompanied by uric acid and other 
products of deficient oxidation, and characterizes the hyperacid 
state. The ammonia may be detected by a microscopical ex- 
amination of the dried saliva, although the ammonium salts 
do not polarize light (Plate VIII, Fig. i, page 327), also by the 
reaction with Nessler's reagent, which produces a yellow color. 

Potassium Sulphocyanate is peculiarly a constituent of the 
saliva, although it occurs in traces in the blood, urine, etc. 
In a state of health, according to Dr. Michaels, the ammonium 
salts and the sulphocyanates are present in very slight amounts, 



5IO DIGESTION 

and the color-tests, with Nessler s solution and with ferric chlorid, 
respectively, are of about equal intensity. In the hyperacid 
state the sulphocyanates are in excess of ammonia, while in 
hypoacid conditions, the ammonia exists in the greater quan- 
tity. Sulphocyanate is detected by means of ferric chlorid, 
and distinguished from meconates and acetates, as indicated 
by Exp. 216 page 329. The sulphocyanates are normal con- 
stituents of saliva, and consequently always present. According 
to A. Mayer (Deutsch. arch. f. klin. med., Vol. 79, No. 394), 
the sulphocyanates, without doubt, result from the decomposi- 
tion of proteins, and exist in the urine in quantities variously 
estimated from 20 to 80 milligrams per liter, while in saliva it 
has been estimated from 60 to 100 milligrams per liter. Professor 
Ludholz of the University of Pennsylvania says that the sulpho- 
cyanates are eliminated in increased amounts in conditions 
where there is a lack of oxygen in the system, thus corrobo- 
rating statements of Professor Michaels (see Ammonia). Dr. 
Fenwick (Lancet, 1877, Vol. II, page 303) demonstrated that 
the quantity of KCNS was directly dependent upon the bile 
salts in the blood. He found an increase of the salt in liver 
disorders attended with increase of bile salts in the blood, and 
marked increase in jaundice. In gout, rheumatism, and con- 
ditions producing pyorrhoea, it is also claimed to be present in 
considerable quantity. 

The sulphocyanates are usually present in more than normal 
quantity in the saliva of people addicted to smoking tobacco.* 
The claim has been made for this salt that it exerts a specific 
antiseptic action toward bacteria. 

While the sulphocyanates, or, in fact, any salt in sufficient 
concentration, will have an inhibitory action on the growth of 
bacteria, it is rather doubtful if this is the particular office of 
KCyS in the saliva. 

Nitrites. — That nitrites exist in most salivas is without ques- 

* See article by Dr. J. Morgan Home in Jour, of the Allied Societies, Vol. 4. 
Ms. 3, p. 183. 



SALIVA PROPERTIES AND CONSTITUENTS 311 

tion. So far as we know at present, the nitrites are apparently 
incidental, and occur as intermediate products in the oxidation 
of ammonia to nitrates, just as they do otherwise in nature out- 
side of the animal body. 

It is not at all improbable that the proportion of nitrates is 
dependent upon activities of the oxidases. This has, in some 
cases at least, been proven to be the case, as the same sample 
of saliva has frequently given steadily diminishing quantities 
of nitrates until they have wholly disappeared in cases contain- 
ing active oxidizing enzymes. 

Oxidases. — As a result of the work of Dr. C. F. Mac- 
Donald in the author's laboratory, the following conclusions were 
reached regarding these enzymes: 

First. That human mixed saliva contains an oxidizing 
enzyme distinct from ptyalin. 

Second. That the enzyme exhibits the properties of both an 
oxydase and a peroxydase. 

Third. That it is a product of the body (probably glandu- 
lar) metabolism and may be increased in quantity, or activity by 
mastication. 

Fourth. That it is more resistant to heat than ptyalin, but 
more easily destroyed by acids. 

Fifth. That the color obtained with a freshly prepared 1% so- 
lution of pyrocatechol is sufficient test for this enzyme in saliva. 

The test for oxidizing enzymes may be made with the pyro- 
catechol as given on page 323 ; also by the use of phenolphthalin 
(reduced phenolphthalein). This last reagent has recently been 
rendered available by the work of Dr. H. L. Amoss, Harvard 
Medical School, who has given us a concise and simple method 
for its preparation. (Jour. Biolog. Chem., 191 2.) 

Phosphates and Carbonates. — These salts are probably pres- 
ent in both acid and neutral forms; that is, the phosphate may 
exist as Na 2 HP0 4 also as NaH 2 P0 4 , and at times both of these 
may be present at once. The acid carbonate, NaHC0 3 , is an 



312 DIGESTION 

undoubted constituent, while the neutral carbonate is present in 
only very slight quantities, if at all. Chittenden says that mixed 
human saliva contains normally no sodium carbonate whatever. 

As explained by Dr. Kirk, the normal reaction by which 
overacidity of the blood is taken care of by renal epithelium 
is H 2 C0 3 + Na 2 HP0 4 = NaH 2 P0 4 + NaHC0 3 , and when con- 
ditions are such as to produce larger quantities of carbonic acid 
than the kidneys can eliminate in accordance with the above 
reaction, there is an increased acidity of the saliva as well as of 
the urine.* In the hypoacid individual, the so-called alkaline 
sodium phosphate, Na 2 HP0 4 , is present in the greater quantity. 
In diabetic patients, sugar has very rarely been found in the 
saliva; one case coming under the observation of the author 
was that of a woman of middle age, with diabetes of long stand- 
ing, with 8% of sugar in the urine, and from this case there were 
obtained a very few osazone crystals by subjecting a consider- 
able quantity of saliva, after concentration, to the phenyl- 
hydrazine test. 

Urea has been repeatedly found in the saliva of patients 
suffering from chronic nephritis. 

Acetone is of quite frequent occurrence in the saliva. In 
diabetic patients this substance is often present in compara- 
tively large amounts, sometimes sufficient for the detection of 
the acetone by its characteristic odor. Acetone may appear in 
the saliva when it is not present in the urine. In such cases it 
has usually resulted from disordered digestion and a consequent 
faulty metabolism. (For further consideration of acetone, see 
Urine.) 

Cholesterin and lecithin have been found by Professor 
Michaels in pathological saliva, and leucin has been found by 
Michaels in a case of lupus and, according to Novey, in a case 
of hysteria. 

Of the crystalline salts which may be separated by evapora- 

* International Dental Journal, February, 1904. 



SALIVA PROPERTIES AND CONSTITUENTS 313 

tion of dialyzed saliva, the sodium oxalate and the lactates and 
acid lactates of lime and magnesia are of the most impor- 
tance and have been the most thoroughly studied. As these 
salts may likewise be separated from urine their significance will 
be studied under that head. 



CHAPTER XXXIV. 
ANALYSIS OF SALIVA. 

The analysis of saliva may be taken up from two distinct 
Standpoints, and considering our present lack of positive knowl- 
edge on this subject it may for a while be expedient so to study 
it. First, we will study a few tests of saliva of such a character 
that they may be made with simple apparatus, and which might 
be used by any dental practitioner with sufficient time and interest, 
to contribute to our general knowledge ; secondly, we may study 
saliva by accurate laboratory methods which are not available 
for general use, but which are necessary for the establishment of 
positive data, and in fact necessary for an intelligent schedule 
of tests under division I. 

At least two methods are therefore to be considered. The 
second method should include the standard methods of the 
National Association but of course is not necessarily confined 
to them. 

We shall introduce a third method in some cases, which will 
be supplementary to the second. 

As it is quite important that the division of salivary analysis 
into these three methods be clearly understood the following 
definite classification is given. 

Methods marked I are in large part taken from Professor 
Michaels' methods, and are the simplest methods applicable to 
small amounts. They will give results of various degrees of 
value, but may be applied in a few moments by any dentist. 

Methods marked II are those given by Dr. Ferris and 
adopted by the National Dental Association at its annual meet- 
ing in 191 1, and reported in the Dental Cosmos for November 
of that same year, on pages 1295, etc. 

314 



ANALYSIS OF SALIVA 315 

Methods marked III are those which the author believes to 
be the most accurate and the most satisfactory in exhaustive 
determinations. 

Physical properties of the saliva should first be noted. In 
method I, the color and appearance of the perfectly fresh sample 
is to be carefully compared with the appearance and color after 
standing for forty-eight hours in a small, tightly covered vial. 
The color may be yellowish, greenish, or brown, according to 
the variety of the derivative of biliverdin from which the color 
is obtained.* The general appearance may also change inde- 
pendently of any color. A saliva that is, when fresh, hypoacid 
in character, is, after forty-eight hours, usually markedly opales- 
cent and of offensive odor, while a hyperacid saliva may have 
become clear or cloudy but without odor. 

By method II, we should add to this examination a viscosity 
test which will be of value as indicating the amount of mucin, as 
probably the mucin content affects the viscosity more than any 
one constituent. 

The viscosity may be determined by use of the apparatus 
pictured in Fig. 21 (page 316). 

The essential features of the viscosimeter are a straight grad- 
uated tube with the constriction (c) jacketed so that the condi- 
tions under which a given sample will pass through the opening 
will always be under absolute control. 

The apparatus is standardized by partly filling with dis- 
tilled water in which the bulb of a thermometer is immersed. 

The temperature of the distilled H 2 is brought to 25 C. The 
thermometer is removed to facilitate reading and from 5 to 10 
c.c. of the liquid are allowed to run out, the time consumed 
being accurately determined by a stop watch. 

The viscosity of saliva is determined in the same way, except 
that this sample must be strained through a very fine brass 

* Dr. Joseph P. Michaels. S. S. White's reprint of paper read before Inter- 
national Dental Congress, Paris, 1900. 




Fig. 21. 



316 



ANALYSIS OF SALIVA 



317 



sieve (100 meshes to the inch) to prevent clogging of the appa- 
ratus. 

If the constriction of the graduated tube is sufficiently 
great, i.e., the opening sufficiently small, comparison may be 
made by counting drops delivered in a given time. This is 
not advised, as there is much greater difficulty in obtaining 
the saliva free enough from suspended particles so as not to 
clog the tube. 

The inner tube should always be filled to the same mark in 
the determination as that used in the standardization of the 
instrument. 

The reaction may be taken in method I by the simple use 
of litmus paper. This test has a general 
value, and is sufficient to detect extreme 
conditions. Our second method should 
be, in this case as in most others, a quan- 
titative one, and the degree of alkalinity 
should be determined by titration with 
N/20 or N/100 acid, using a strong prac- 
tically neutral litmus solution as an in- 
dicator. The degree of acidity, using N/20 
or N/100 alkali and neutral phenol- 
phthalein as an indicator, should be deter- 
mined next. Then the reaction, after driv- 
ing off carbon dioxid, should be ascertained. 
The permanent acidity, if such exists, 
should be found a useful factor in the study 
of Dental Caries and may be determined 
by the apparatus pictured on page 305. 

Specific Gravity may be taken (Method I) by an ordinary 
urinometer or a specific gravity bulb if the quantity is sufficient, 
the reading to be made from beneath the surface of the liquid. 
If the quantity of the saliva is small, it may be diluted with an 
equal volume of water, and the last two figures multiplied by 




Fig. 22. — Pyknometer. 



3i8 



DIGESTION 




Fig. 23. 






two will give the gravity of the undiluted sample, or the gravity- 
may be taken by the pyknometer in which the bulb of the instru- 
ment is filled with saliva accurately to the mark M (Fig. 22), 

and then the reading of course on this instrument will be from the 

bottom up, and the lower the bulb 
sinks the greater will' be the gravity 
of the sample. This method, claimed 
to be devised by S. A. De Santos 
Saxe, M. D., for use in examination 
of urine, has been suggested by Dr. 
Ferris and adopted by the National 
Dental Association as an official 
method. 
For very accurate work the use of specific gravity bottles is 

recommended. These may be obtained holding one, two and 

five cubic centimeters (Fig. 23), and with an 

accurate balance of course the gravity can 

be accurately obtained. 

Thiocyanate (Sulphocyanate) Tests. — 

(Method I.) To a large drop of saliva on 

a white porcelain surface, add about half 

as much 5% ferric chlorid, acidified with 

HC1. A reddish coloration indicates the 

presence of thiocyanate. " (Method II.) 

Use a colorimetric scale (Ferris and Schra- 

dieck), place 1 c.c. of the specimen in tube 

A ; 1 c.c. of 1/2000 ammonia sulphocyanate 

in tube B (Fig. 24) ; add two drops of a 5% 

ferric chlorid solution to each tube, add 

aquo distillata in tube B, until its color 

matches that of the specimen. Read the 

scale in thousandths and ten thousandths. 

"Care must be taken to have the bottom of the meniscus 

on the line. If these tubes are introduced in the colorimeter, 



Fig. 24. — Sulphocyanate 
Tubes. 



ANALYSIS OF SALIVA 319 

the readings can be made more accurately. If, later, diacetic 
acid ester is found, a correction is made in the finding. " 

A much more accurate method than either of these is by use 
of the Duboscq colorimeter, the detail of the method being as 
follows : 

(Method III.) Fifteen cubic centimenters of a standard thio- 
cyanate solution is placed in one tube, and in the other a filtered 
mixture of equal parts of saliva and alcohol made fairly acid 
with HC1. Then two or three drops of acid ferric chlorid are 
added to each tube, and the color compared. Scale on the back 
of the instrument makes it possible for very accurate deter- 
minations of quantity of the color compound in the unknown 
solution. 

Ammonium Salts. — (Method I.) To a drop of saliva add 
one drop of Nessler's reagent: a yellow to brown color shows the 
presence of ammonium salts. If a precipitate forms by the 
addition of Nessler's reagent, it indicates either a large amount 
of ammonia or the presence of urobilin. If due to urobilin the 
precipitate is of a rose color after desiccation. Ammonium salts 
are usually seen in the evaporated drop examined by polarized 
light. (Plate VIII, Fig. 1.) 

(Method II.) Add one drop of neutralized 1% solution of 
phenolphthalein to 2^ c.c. saliva, and titrate with N/40 NaOH 
solution to a permanent color of faintest pink. Ten times the 
number of cubic centimeters of NaOH used gives the acid index, 
since N/40 : N :: 2.5 c.c. : 100 c.c, and the acidity is expressed 
in parts per liter (1000 c.c). 

Now add to the above 1 c.c of neutralized formalin. The 
pink color disappears, because the formalin splits off ammonia 
from the organic matter, liberating free acids. Titrate again to 
find the amount of combined acids thus liberated, and multiply 
the reading by 10 as before. 

Total acidity is obtained by adding the two findings. 



320 



DIGESTION 



Amino-acids calculated as ammonia may be obtained by 
multiplying the second findings by 0.0017. 

(Method III.) A modification of Dr. Folin's ammonia test 
in urine, using the Duboscq colorimeter. 

Measure out 10 c.c. of saliva in a large Jena test-tube. Add 
2 c.c. of a solution containing (a) potassium oxalate, (b) potassium 
carbonate (15% of each). By means of an air cur- 
rent, drive the ammonia through a Folin absorption- 
tube (Fig. 25) into a 100 c.c. wide-mouth bottle 
containing 2 c.c. N/10 HO, and about 30 c.c. water. 
In 20 minutes, all the ammonia should have gone over. 
Remove the delivery-tube, rinsing it with water, 
and transfer contents of bottle to 100 c.c. measuring 
flask, rinsing with sufficient water to make total 
volume about 60 c.c. 

Pipette out 1 c.c. of standard ammonium sul- 
phate into another 100 c.c. measuring flask and 
dilute with water to about 60 c.c. 

Nesslerize both solutions simultaneously in the 

following manner. Provide two small beakers (100 

c.c.) and place from 10 to 15 c.c. of distilled water 

in each. Add to each 5 c.c. of Nessler's reagent. 

Mix the reagent with water, and add immediately 

to the ammonia solutions. Add about one- third of 

the diluted Nessler reagent at a time, and shake 

after each addition. 

Fill both flasks up to mark with distilled water, mix and 

compare the colors by means of a Duboscq colorimeter (Fig. 20, 

page 307). 

Urea. — Reagent, sodium hypobromite as used for urea in 
urine analysis (Appendix, page 380). 

Fill the tube of a Ferris modified Doremus ureometer with a 
saturated salt solution. Close the stopper, and add 1 c.c. of 
saliva to the upper tube. Allow this to run through the stopper 




Fig. 25. 



ANALYSIS OF SALIVA 321 

carefully, then close, and add 1 ex. of the reagent. When this 
has gone through, close the stopper quickly, set up the apparatus, 
and allow to stand one hour or longer. Then, by gently tapping, 
cause any bubbles adhering to the sides of the tube to rise to the 
top, and read the amount of gas collected. Each division repre- 
sents 0.025. 

Chlorids. — (Method I.) To a drop of saliva add a small drop 
of a 5% solution of neutral chromate of potassium, K 2 Cr0 4 . Mix 
with a glass rod and add one drop of a 1/10% solution of silver 
nitrate. This constitutes the test for chlorin which, if present 
in normal quantities, will give a reddish precipitate, gradually 
becoming white. Should the precipitate remain red it shows 
the chlorin deficient or less than normal in amount. If the 
precipitate rapidly turns white, or if a white precipitate is 
formed to the exclusion of the red, chlorin is increased in amount. 
High chlorin is indicative of hypoacid diathesis. 

(Method II.) To 1 c.c. of the specimen add 4 c.c. of distilled 
water and two or three drops of potassium chromate; then 
titrate with N/40 silver nitrate solution, until the first appear- 
ance of a permanent reddish tinge. Multiply the number of 
cubic centimeters of nitrate used by 0.0886 to find the amount 
of chlorin. 

Glycogen. — (Method I.) A drop of saliva may be tested 
for glycogen by the addition of one drop of an aqueous solution 
of iodin and potassium iodid. This must be left for some time, 
as the test is not obtained until the drop is dried; then, if the 
color is a feeble violet around the edge, glycogen is indicated. 
If the color is a strong brown-red it indicates erythrodextrin, 
if gray or black a reducing sugar. 

Phosphates. — The phosphates in saliva are determined as 
in urine except that it is necessary to modify the process slightly 
as given on page 153. 

Acetone. — (Methods I and III.) In the fifth drop dissolve 
a small crystal of potassium carbonate, then add a drop of 



322 DIGESTION 

Gram's reagent, when a marked odor of iodoform will indicate 
the presence of acetone. Should this odor be obtained, it is 
better to repeat this test upon a microscope slide, and examine 
carefully for the characteristic hexagonal crystals of iodoform 
(Plate V, Fig. i, page 222). 

Nitrites. — (Method I.) Nitrites may be detected by add- 
ing to a large drop of saliva on porcelain a few drops of freshly 
prepared reagent, made by dissolving a very little naphthylamin 
chlorid and an equal amount of sulphanilic acid in distilled water 
strongly acidulated with acetic acid. A purple coloration is a 
test for nitrites. 

This method could be made quantitative in a manner simi- 
lar to the colorimetric methods for ammonia, or thiocyanate 
of potassium; but, at the time of the present writing, there 
seems to be no particular reason for this amount of work. 

Amylolytic Enzymes. — (Method II.)* Preparation of starch 
paste. Put 15 c.c. of distilled water to boil. Meanwhile, weigh 
out 3 grams sterile starch and mix with 6 c.c. cold distilled 
water. Add drop by drop under constant stirring to the boiling 
water, then rinse out with 5 c.c. of distilled water any particles 
of starch adhering to the dish and add to the boiling starch solu- 
tion. Boil one minute under constant stirring. Cool to blood 
temperature and add gradually 4 c.c. of N/100 iodin solution. 

This makes 30 c.c. of a 10% starch solution, which, when 
colored, is of a dark blue, and can be kept several days in the 
ice-box. 

Filling the Tubes. — Suck up the paste into glass tubes of 
1.5 mm. diameter, and cool in the ice-box. Just before using, 
make a file mark 1 cm. from the end of the tube and break off 
the piece of tubing so that it is full of the blue starch paste. 
Be sure that this small tube is broken so as to leave each end 
square and full of paste. Examine under low-power microscope. 

Determination of Enzyme. — Immediately after delivery of 

* Method II as usual by Dr. Ferris (see p. 314). 



ANALYSIS OF SALIVA 323 

the specimen, measure 2 c.c. of saliva into a test-tube. Place 
it in the small tube of starch paste, and heat the whole in a 
thermostat at from 37 to 38 C. for half an hour. The enzyme 
of the saliva will dissolve the paste from the ends of the tube, 
leaving a blue column of paste unchanged in the center of the 
glass tube. After half an hour, measure with a micrometer 
gauge the total length of the tube and the length of the blue 
starch paste column remaining undissolved. The difference 
between these two measurements represents the amount of starch 
digested by the enzyme. Since the quantity of ferment in any 
fluid varies with the square of the length of the column digested, 
the quantity of ferment in the saliva is found by squaring 
this difference. Multiply by 100 to give the enzymic index. 

Proteolytic Enzyme. — (Method II.) Reagent. Dissolve 1 
dg. of casein (c.p.) and 1 gram sodium carbonate in 1 liter of 
distilled water. Mix 1 or 2 c.c. Fehling's copper solution and 
5 c.c. Fehling's alkaline solution, and add the mixture to 94 c.c. 
of the first solution. The color will be a light blue. 

Heat 5 c.c. of the reagent in the thermostat at from 37 to 
38 C. Then add 1 or 2 c.c. saliva, and watch the color. If 
there is a strong reaction, the color will turn pink in five seconds, 
indicating the presence of peptone. If the reaction is medium, 
a lavender color will result, indicating albumin. If there is no 
reaction, the color will remain a dirty blue, and will indicate 
unsplit casein. 

Oxidizing Enzyme. — (Oxydase.) Methods I and III con- 
sist of treating 5 c.c. of saliva, diluted with an equal volume of 
water, with about 1 c.c. of a 1% solution of pyrocatechol. The 
color obtained is a characteristic brown, developing within 
thirty minutes. 

Oxydase. — (Method II.) Take 1 c.c. of saliva, 4 c.c. of 
aqua distillata, twelve drops of a 10% solution of H 2 S0 4 , then 
mix and add drop by drop 0.5% water solution of metaphenylene- 
diamin. If there is no oxydase, it stays without color. If there 



324 DIGESTION 

is an oxydase, there is formed triaminphenylin, which makes the 
solution strongly yellow. Compare the color formed with four 
drops and ten drops standard in aqua distillata.* 

Mucin and Albumin. — (Method I.) Mucin may be sepa- 
rated after taking the gravity by the addition of a little acetic 
acid. It should then be filtered off, but it will be necessary to 
dilute and agitate, in order that a fairly clear filtrate may be 
obtained. 

Albumin may be demonstrated in the filtrate, from which 
mucin has been separated by underlaying with strong nitric 
acid. This is Heller's test for albumin in the urine, and is best 
performed in a small wine-glass with round bottom and plain 
sides. 

Mucin, Albumin and Sediments. — (Method II.)* I. Cen- 
trifuge 10 c.c. of the specimen of saliva for three minutes in a 
tube graduated to fortieths. Record the amount, percentage, 
and color of the sediment. Pour off and save the supernatant 
fluid; record its appearance. 

II. To the precipitate add 10 c.c. of limewater, shake vigor- 
ously, and let stand for five minutes. Shake again and centrifuge. 
The difference between the total sediment and this reading gives 
amount of mucin and nuclear albumin which the limewater has 
dissolved. Record the percentage of the mucin in the sediment. 

III. To 2 c.c. of the fluid saved from I add 8 c.c. distilled 
water. A cloudy appearance indicates the presence of globulin. 
Centrifuge, and record the amount. 

IV. (a) To the fluid remaining from II add io drops of 
glacial acetic acid. A precipitate indicates dissolved mucin. 
Centrifuge, and record the amount and percentage of mucin. 

(&) If the saliva is thin, and if it gives only a trace of dissolved 
mucin that settles easily, repeat, using the whole of the liquid 
remaining from I. Save the liquid, and subtract the amount 
of globulin from the percentage of the precipitated mucin. 

* Dr. H. C. Ferris. 



ANALYSIS OF SALIVA 325 

(c) If the saliva is viscid, and if it becomes cloudy in (a) 
without the separation of a precipitate, take 2.5 c.c. of the 
liquid remaining from I, add 7.5 c.c. neutralized 95% alcohol, 
shake well, and let stand for rive minutes. Then centrifuge and 
record the amount of dissolved proteins in the saliva. Pour of! 
and save the liquid. 

Add limewater to the precipitate, shake well, let stand for 
two or three hours, and centrifuge to determine the amount of 
mucin dissolved from this precipitate. 

V. (a) To the liquid remaining from IV (a), or IV (b) add 
1 c.c. of 10% solution of potassium ferrocyanid. If albumin is 
present, the specimen will become cloudy. Centrifuge as before, 
and record the amount of albumin. 

(b) To the liquid remaining from IV (c) add 1 c.c. nitric 
acid to see if there be a precipitate. 

Also to the liquid in IV (a), when the precipitate will not 
settle, add 1 c.c. of 10% solution of potassium ferrocyanid and 
centrifuge. Subtract the amount of mucin found in IV (c) to 
find the quantity of albumin. 

Total Solids and Ash. — (Method II.) These should be de- 
termined immediately upon the arrival of the specimen to avoid 
error through evaporation of moisture. 

Use a platinum or fused silica dish of constant weight which 
has been kept in a desiccator over sulphuric acid. Weigh the 
dish accurately and rapidly, then introduce 2J c.c. of the well- 
mixed specimen and heat in a drying oven, not over ioo° C, for 
two hours. Then place in the desiccator over sulphuric acid 
for twelve hours or longer, and weigh accurately and rapidly. 

The difference between these weights represents the weight 
of total solids. To calculate the percentage, divide by two and 
one-half times the specific gravity. 

Add to the dish two or three drops of fuming nitric acid, 
and heat over a flame, keeping the dish two inches above the 
top of the flame, until the black color has become white. Heat 



326 DIGESTION 

in the direct flame until glowing, place at once in desiccator to 
cool for one or more hours, and weigh. Calculate the percentage 
of ash in same manner as of total solids. 

(Method III.) Total solids and ash are best obtained as 
follows: evaporate over a water bath 5 c.c. of the sample (10 if 
possible) thoroughly mixed with a weighed amount (half a gram) 
of ignited magnesium oxid. The weight of residue (less the 
magnesia) obtained by drying at ioo° C, gives the total solids. 
These may be ignited until white ash is obtained and again 
weighed. The second weight (less magnesia) gives the ash. 

The use of the magnesium oxid serves to retain carbonates 
and chlorids in the total solids and the chlorids in the ash. It 
also obviates the necessity of oxidation with nitric acid, which 
would decompose many of the inorganic constituents of the 
ash. 

To determine weight of sediment. Obtain total solids as 
above; then if a portion of the saliva is carefully filtered and the 
solids determined in the clear filtrate by the same method, 
the difference between the two determinations of solids will be 
the weight of sediment, epithelium, leucocytes, etc. 

Crystals from the Dialyzed Saliva. 

To obtain characteristic crystals, as has been explained in 
considering the subject of micro-chemistry, uniformity as to 
conditions under which the crystallization takes place is a 
necessity. In the case of saliva, however, we are not produc- 
ing new compounds, but simply searching for compounds already 
formed and existing in unknown proportions in the samples 
tested. It is therefore necessary to make several preparations 
of each sample, in order that we may obtain the widest range 
of possibility for characteristic crystallizations. The following 
method of procedure will usually give satisfactory results: For 
a dialyzer use a fairly wide glass tube, over one end of which 
has been tightly tied a piece of parchment (Fig. 26), or better, 



PLATE VIII. — ANALYSIS OF SALIVA. 




Fig. i. 
Ammonium Chloride. 




FIG. 3- 
A, Magnesium Lactate (P. L.). 
B, Calcium Lactate (P. L.). 





Fig. 2. 
Sodium Chloride, |%. 




Fig. 4. 
A, Magnesium Acid Lactate. 
B, Calcium Acid Lactate. 




Fig. 5. 
Potassium Chlorid, \% Solution. 



Fig. 6. 

Potassium Chlorid, \% Solution. 



ANALYSIS OF SALIVA 



327 



a small dialyzing tube made entirely of parchment. Place 
about 15 ex. of saliva in the dialyzing tube, and suspend it in 
a small beaker or wine-glass which contains an equal volume of 
distilled water. At the end of twenty-four hours the distilled 
water will contain the dialyzable salts in nearly the same con- 
centration as existed in the original saliva. Take four previ- 
ously prepared cell-slides (microscope 
slides on which a ring of Bell's or 
other microscopical cement has been 
placed) and fill each cell full of the 
dialyzed saliva. Put number 1 in a 
warm place that it may evaporate 
rapidly, leave number 2 exposed to 
the air at the room temperature and 
it will dry in from half to three- 
quarters of an hour. Place number 
3 under a large beaker, or small bell- 
jar, and cover number 4 with a cover- 
glass, and from time to time examine 

the crystals that may be formed. Numbers 3 and 4 will prob- 
ably take several hours, perhaps several days, before crystal- 
lization is complete. When the crystals have appeared, the 
preparation may be preserved by mounting in xylol balsam. 
In attempting to obtain crystals from the saliva before dialy- 
zation, results are usually unsatisfactory, owing to the presence of 
mucin and other organic substances which interfere with the crys- 
tallization. The crystals obtained by this method are principally 
sodium oxalate, lactates, and acid lactates of lime and magnesia, 
and rarely urates of the alkalis. (For forms of these crystals see 
Plate VIII, Figs. 3 and 4, and Plate II, Fig. 4, pp. 327 and 162.) 




Fig. 26. 



Laboratory Exercise LXX. 

Exp. 214. Action of Saliva upon Starch. — Take some fil- 
tered saliva in a test-tube and place in the water-bath at 40 C, 



28 DIGESTION 



for five or ten minutes. Put some starch paste into a second 
test-tube and place this also in the water-bath for a while, then 
mix the two (10 c.c. of starch paste to 3 c.c. of undiluted saliva) 
and return to the water-bath. The starch is changed first to 
soluble starch (if originally a thick paste, it becomes fluid and 
loses its opalescence), then to erythrodextrin, which gives a 
red color with iodin, and finally to achroodextrin, which gives 
no reaction with iodin, and to maltose. Prove these changes 
as follows: Every minute or two take out a drop of the mix- 
ture, place it on a porcelain plate, and add a drop of iodin solu- 
tion. This gives first a blue color, showing the presence of 
starch; later a violet color, due to the mixture of the blue of 
the starch reaction with the red caused by the dextrin; next a 
reddish-brown color, due to erythrodextrin alone (starch being 
absent), and finally no reaction at all with iodin, proving the 
absence of starch and erythrodextrin. The fluid now contains 
achroodextrin and maltose. Test for the latter with Fehling's 
solution and with Barfoed's reagent. 

Exp. 215. Influence of Conditions on Ptyalin and its Amylo- 
lytic Action. — Report and explain the results of the following 
experiments : 

(a) Boil a few cubic centimeters of the saliva, then add 
some starch paste, and place in the water-bath at 40 C. After 
five minutes test for sugar. 

(&) Take two test-tubes: put some starch paste in one, and 
saliva in the other, and cool them to o° C, in a freezing mixture. 
Mix the two solutions, and keep the mixture surrounded by 
ice for several minutes, then test a portion for sugar. Now 
place the remainder in the water-bath at 40 C, and after a 
time test for sugar. 

(c) Carefully neutralize 20 c.c. of saliva with very dilute 
HC1 (the 0.2% diluted), and dilute the whole to 100 c.c. Test 
the action of this neutralized saliva on starch. 

id) To 5 c.c. of starch paste add 10 c.c. of 0.2% HC1 and 



ANALYSIS OF SALIVA 329 

5 c.c. of neutral saliva, and expose the mixture for a while at 
40 C, and test for sugar. 

(e) To 5 c.c. of starch paste add 10 c.c. of a 0.5% solution 
of Na 2 C0 3 and 5 c.c. of neutral saliva, and expose the mixture 
for a while at 40 C, and test for sugar. 

(/) Carefully neutralize (d) and (e) , and again test the action 
of the two on starch. 

(g) Mix a little uncooked starch with saliva, expose to a 
temperature of 40 C. for a while, and test for sugar. 

Exp. 216. In three separate test-tubes place a few cubic 
centimeters of dilute solutions of KCNS or NH4CNS, of meconic 
acid, and of acetic acid; add to each a few drops of ferric chlorid, 
and notice that a similar color is obtained in each case. Divide 
the contents of each tube into two portions, and to one set add 
HC1; to the other add mercuric-chlorid solution. Formulate a 
method of distinguishing from the sulphocyanates, meconates, 
and acetates. 

Tests for Abnormal Constituents. 

Acetone, glycogen, and dextrin have already been con- 
sidered. Urea may be demonstrated as follows: To a given 
volume of saliva add twice as much alcohol. This serves to 
precipitate proteins. Filter and evaporate on a water-bath till 
original volume is reached, or evaporate to less than original 
volume, and make up with distilled water. Then determine urea 
with Squibb 's apparatus, as used for urine, except that in this 
case it will be necessary to replace the 2-c.c. pipette with a small 
burette, and introduce 10 c.c. of the prepared saliva. Then it will 
be necessary to allow for these 10 c.c. by subtracting this amount 
from the volume of water received in the graduated cylinder, and 
the remaining number of cubic centimeters, multiplied by two, 
will correspond to the urea in 20 c.c. of the sample. The percent- 
age shown on the card, divided by ten, will give the per cent of 
urea required. See also method by Dr. H. C. Ferris on page 320. 



330 DIGESTION 

Lactic, butyric, and acetic acids may each be tested for, quali- 
tatively, by the methods given under gastric digestion (q. v.). 

Mercury. — A very delicate test may be made for this metal 
as follows: Collect as large a sample of saliva as possible, dilute 
with an equal volume of water, acidify with a few drops of 
HO, throw in a few very small pieces of copper-turnings, which 
have been recently cleaned in dilute HN0 3 , and boil for at 
least one-half hour, keeping up the volume by occasional addi- 
tions of water. Remove the copper-filings, dry thoroughly on 
filter-paper, and place in a large-sized watch-glass (3 inches). 
In another watch-glass of similar size place one drop of solu- 
tion of gold chlorid, and quickly invert so that the drop remains 
hanging on the under side of the glass. Now place this watch- 
glass directly over the one containing the copper, so that the 
chlorid of gold shall be suspended directly above the turnings 
and perhaps a half inch from them, then gently heat the lower 
watch-glass with a very small flame, when the slightest trace 
of mercury, which may have been deposited upon the copper, 
will be volatilized, reducing the chlorid of gold, and causing a 
purplish ring to appear around the edge of the drop. If no 
reduction of the gold occurs, mercury is absent. 

Lead, which occasionally occurs in saliva, may be detected 
by the methods given under urine. 

Microscopical examination of the sediment should be made 
in every instance. Normal saliva will contain epithelium from 
various parts of the oral cavity, an occasional leucocyte, and 
occasional mold fungi, leptothrix, etc. Constituents, which per- 
haps are not properly classed as normal and at the same time 
are not pathological, are fat globules, a rare blood-corpuscle, 
sarcinae, extraneous material as food particles, starch granules, 
muscle fibers, etc. An excessive amount of blood, fat, pus, or 
micro-organisms would, of course, indicate pathogenic conditions. 
The bacteriological investigation of samples of saliva is always 
of interest, and may be necessary, but the detailed methods of 
such investigation do not lie within the scope of this work. 



CHAPTER XXXV. 
GASTRIC DIGESTION. 

Digestion begins with the action of the saliva upon the 
carbohydrates, and if mastication is sufficiently prolonged, the 
ptyalin may convert an appreciable quantity of starchy food 
into a more soluble form before it reaches the stomach. In the 
stomach the amylolitic action of the saliva is stopped by the 
contact with the gastric juice. A certain amount, however, of 
salivary digestion takes place within the stomach, due to the 
fact that considerable time necessarily elapses before the acid 
of the gastric juice has been secreted in sufficient quantity to 
completely permeate and acidify the mass of food received 
from the oesophagus. As has been previously shown, a very 
feeble degree of acidity is conducive to the activity of the 
amylolytic ferment. The average alkalinity of the saliva, cal- 
culated as Na 2 C0 3 , is about 0.15 of 1%. 

The first step in the gastric digestion is probably the union 
of the stomach HC1 with the proteins, forming acid albumins 
(metaproteins) or allied bodies which are changed by pepsin, 
which is the active digestive ferment of the stomach, into the 
albumoses (proteoses), and slight amounts of the various pep- 
tones, following practically the changes produced experimentally 
on page 332. 

Pepsin is an active proteolytic enzyme occurring in the cells 
of the stomach- wall as pepsinogen, which is decomposed by 
the HC1 with the formation of free pepsin. Pepsin works only 
in faintly acid solutions, and in the stomach carries the diges- 
tion of proteins but little beyond the stage of the proteoses. 

Hydrochloric acid is obtained from the fundus glands by an 

33 1 



332 DIGESTION 

interchange of radicles between alkaline chlorids and the car- 
bonates of the blood.* The quantity present varies from o to 
3/10 per cent, 0.18% being about the most favorable for peptic 
activity. Aside from HO, various organic acids may be pres- 
ent in the stomach contents; lactic acid, butyric acid, and acetic 
acid are the most important of this class, tests for which are 
referred to under analysis of gastric contents. 

Hydrochloric acid combines with protein substances of the 
food, forming a rather unstable compound in which condition 
the acid is known as combined hydrochloric acid in distinction 
from the free hydrochloric acid which the gastric juice may also 
contain. The combined HC1 possesses only in modified form 
the properties of free HC1, and hence is less liable to stop the 
digestive action of ptyalin from the saliva. 

Rennin is a second enzyme found in the stomach. This, like 
pepsin, also exists as a zymogen, and is liberated or developed 
by the presence of acid. Its action is particularly the curdling 
of milk, i.e., the decomposition of caseinogen (Exp. 222), and 
consequent coagulation of the casein. A third enzyme, existing 
in the stomach in very small quantities, is a gastric lipase, or 
stomach steapsin, a fat-splitting enzyme, the action of which 
is comparatively weak and of but slight importance. 



Laboratory Exercise LXXI. 
Analysis of Gastric Contents and Experiments with Pepsin. 

The following solutions will be found in the laboratory: 

A. A 0.2% Solution of HCl. — This is prepared by diluting 
6.5 c.c. of concentrated HCl (sp. gr. 1.19) with distilled water 
to 1 liter. 

B. A Solution of Pepsin. — Prepared by dissolving two 
grams of .pepsin in 1000 c.c. of water. 

* Long's Physiological Chemistry. 



GASTRIC DIGESTION 333 

C. A Pepsin-hydrochloric-acid Solution. — Prepared by dis- 
solving two grams of pepsin in 1000 c.c. of solution A. 

Or, add to 150 c.c. of solution A about 10 c.c. of the glyc- 
erol extract of the mucous membrane of the stomach. 

Exp. 217. Take five test-tubes and label a, b, c, d, e. Fill 
as indicated below. Place in a water-bath at 40 C, and 
examine an hour later, and again the next day. 

(a) 3 c.c. pepsin solution + 10 c.c. water + a few shreds of 
fibrin. 

(b) 10 c.c. 0.2% HC1 + a few shreds of fibrin. 

(c) 3 c.c. pepsin solution + 10 c.c. 0.2% HO, and a few 
shreds of fibrin. 

{d) 3 c.c. pepsin solution + 10 c.c. 0.2% HC1, boil, and then 
add a few shreds of fibrin. 

(e) 3 c.c. pepsin solution + 10 c.c. 0.2% HC1, and a few 
shreds of fibrin which have been tied firmly together into a 
ball with a thread. 

Make a note of all changes. 

Exp. 218. Filter c. Neutralize with dilute Na 2 C0 3 . Filter 
again. Why? Test the filtrate for the biuret reaction. 

Exp. 219. To 5 grams fibrin add 30 c.c. of the pepsin solu- 
tion and 100 c.c. 0.2% HC1. Set in the water-bath at 40 C, 
stirring frequently, and leave in the water-bath overnight. 
Observe the undigested residue, on the following day, and also 
a slight flocculent precipitate. What is this precipitate? 

Filter and carefully neutralize the filtrate. A precipitate 
varying with the progress of the digestion will form. What 
is it? 

Remove this by filtration, and saturate this filtrate with 
(NH 4 )2S0 4 . Filter. Save precipitate and filtrate. Of what 
does each consist? 

Exp. 220. Dissolve the last precipitate of Exp. 219 in water, 
and try the following tests: 

(a) Biuret reaction. 



334 DIGESTION 

(b) Effect of boiling. 

(c) Test with NH0 3 , as in performing test for albumin in the 
urine, page 359. 

Exp. 221. To the last filtrate of Exp. 219 add an equal vol- 
ume of 95% alcohol, and stir thoroughly. The peptones will 
collect in a gummy mass about the stirring-rod. 

(a) Determine the solubility of peptones in water. 

(b) What is the effect of heat when so dissolved ? 

(c) Try the biuret reaction. 

Exp. 222. Demonstration of the Rennet Enzyme. — Place 
10 ex. of milk in each of three test-tubes. Label the test-tubes 
h 2, 3. 

To 1 add a drop of neutralized glycerol extract of the 
mucous membrane of the stomach (made from the stomach of 
the calf). 

To 2 add a drop of neutralized glycerol extract, and boil 
at once. 

To 3 add a few cubic centimeters of (NH 4 ) 2 C 2 04 solution, 
and then a drop of a glycerol extract. 

Place these tubes in the water-bath at 40 C, and examine 
after five to ten minutes. Explain results in each case. 

Continue heating tube 3 for half an hour, then add 2 or 3 
drops CaCl 2 solution. The liquid instantly solidifies. Why? 

Exp. 223. Digestion of Casein. — Determine the products of 
the digestion of the curd from the last experiment. 

Exp. 224. Tests for Free Hydrochloric Acid. — Try each 
of the following tests with (a) HC1 (0.2%, 0.05%, and 0.01% 
successively); (b) lactic acid (1%); (c) mixtures containing 
equal volumes of (a) and (b). Tabulate the results. 

(a) Dimethylaminoazobenzene. — Use one or two drops of a 
0.5% alcoholic solution. In the presence of free mineral acids 
a carmine-red color is obtained. 

(b) Gunzburg's Reagent. — Phloroglucin, 2 grams; vanillin, 
1 gram; alcohol, 100 c.c. Place two or three drops of the solu- 



GASTRIC DIGESTION 335 

tion to be tested in a porcelain dish, add one or two drops of 
the reagent, and evaporate on a water-bath. In the presence 
of free hydrochloric acid a rose-red color develops. 

(c) Boas' Reagent. — This is prepared by dissolving 5 grams 
of resublimed resorcinol and a gram of cane-sugar in 100 grams 
of 94% alcohol. Take three or four drops each of the reagent 
and the solution to be tested, and cautiously evaporate to 
dryness. In the presence of a free mineral acid a rose or Ver- 
million red color is obtained. This gradually fades on cooling. 

(d) Tropceolin 00. — Use one or two drops of a saturated 
alcoholic solution. 

(e) Congo-red. — Use filter-paper which has been dipped into 
a solution of the reagent and then dried. 

Exp. 225. To 5 c.c. egg-albumin in solution add 1 c.c. of 
0.2% HC1. Mix thoroughly, and test for the presence of free 
HC1. What is the result? How do you explain it? Repeat 
the test, using a solution of peptone in place of the egg-albumin. 

Exp. 226. Tests for Lactic Acid. — Uffelmann's reagent. 
Mix 10 c.c. of a 4% solution of carbolic acid with 20 c.c. of 
water, and add a drop or two of ferric chlorid. 

To 5 c.c. of the reagent add a few drops of the lactic-acid 
solution. Note the canary-yellow color. 

Does the presence of free HC1 interfere with this reaction ? 

A more delicate reagent is obtained by adding three or four 
drops of a 10% ferric-chlorid solution to 50 c.c. of water. Such 
a solution has a very faint yellow color, which is distinctly in- 
tensified by lactic acid. 

Using 5 c.c. of this nearly colorless solution for each experi- 
ment, note the effect of (a) 0.2% HC1; (b) acid phosphate of 
sodium; (c) alcohol; (d) glucose; (e) cane-sugar. What con- 
clusions do you reach concerning the value of this test, when 
applied directly to the gastric contents? 

The test is best applied to an aqueous solution of the ethereal 
extract of the gastric contents. Add to the contents two drops 



336 DIGESTION 

of HC1, boil to a syrup, and extract with ether. Dissolve the 
residue obtained upon evaporation of the ether in a little water, 
and test for lactic acid. 

Exp. 227. Test for butyric acid; see ethyl butyrate, page 
207. 

Exp. 228. Test for acetic acid; see acetates (page 94). 

Exp. 229. The acidity of the gastric contents may be deter- 
mined as follows: To 5 c.c. of the filtered contents, diluted with 
25 to 30 c.c. of water in an Erlenmeyer flask, add 2 or 3 drops 
of a solution of dimethylaminoazobenzene. Titrate with N/10 
alkali till the color changes to a yellow which fairly matches 
the indicator; this represents the free HC1. To this mixture 
add a few drops of phenolphthalein solution, and continue the 
titration until a permanent pink color is obtained. The N/10 
alkali used will represent the total acidity, combined HC1 and 
organic acids. The organic acids will not be present in gastric 
contents in the presence of any appreciable amount of free 
HC1, as they are derived almost entirely from fermentations 
which are inhibited by the hydrochloric acid. 



CHAPTER XXXVI. 
PANCREATIC DIGESTION AND BILE. 

It may be an aid, in remembering the various digestive fer- 
ments, to note that in the saliva we have one principal ferment, 
ptyalin; in the stomach we have two principal ferments, pepsin 
and rennin; in the pancreatic juice, three active ferments. The 
first is a proteolytic enzyme, known as trypsin, which continues 
the work of the gastric juice, and converts the proteoses into 
peptones, tyrosin, leucin, etc. 

Trypsin is the proteolytic enzyme of the pancreatic juice. 
It is a much more energetic digestive agent than the pepsin 
found in the stomach, but it differs in that it acts in an alkaline 
media rather than an acid. Trypsin exists, like other proteo- 
lytic enzymes, as a parent enzyme, trypsinogen, which in itself 
is not a digestive ferment, but which is rendered active (acti- 
vated) by another substance known as enterokinase. 

The enterokinase occurs in the intestinal juice, and seems to 
be secreted only as it is needed for the activation of the tryp- 
sinogen. Enterokinase does not in itself possess digestive 
power, but its action is destroyed by heat and in this it resembles 
the enzymes. 

Amylopsin is the starch digesting enzyme of the pancreatic 
juice. Here, again, we have an enzyme much more energetic 
in its action upon carbohydrates than the ptyalin of the saliva. 
It converts starch into maltose and to some extent to dextrin. 
The amylopsin is active in faintly alkaline or very faintly acid 
solution; more acid, however, retards its action. 

Steapsin is the fat-splitting enzyme of the pancreatic juice. 
It splits the fat, as indicated on page 209, into glycerol and 

337 



338 DIGESTION 

fatty acids, and also acts as an emulsifying agent. The free 
fatty acids thus formed unite with the alkaline bases found in 
the intestines to form soaps, which are also active emulsifying 
agents. 

The pancreatic juice and the bile enter the duodenum in 
very close proximity, and the digestive action of each is depen- 
dent, to a considerable extent, upon the presence of the other. 

Bile. — A secretion produced by the liver and stored in the 
gall-bladder, from which it is delivered to the intestines, where 
it aids materially in emulsification and absorption of the fats. 

Composition of Bile. — Its composition is very complex, 
but there are two acids and two coloring matters which are of 
particular importance, and derivatives of which indicate the 
presence of bile in saliva, urine, blood, etc. The acids are 
taurocholic and glycocholic, existing principally as sodium or 
potassium salts. The coloring matters are bilirubin and bili- 
verdin; the former predominates in human bile and the latter 
in ox bile. Glycocholic acid upon hydrolysis splits into a 
simpler acid (cholalic) and glycocoll, glycocoll being an amino- 
acetic acid (page 222), which is undoubtedly an antecedent of 
urea. Both of the bile-pigments are derived from the coloring 
matter of the blood. The appearance of either of these or of 
their derivatives, in either urine or saliva, is indicative of patho- 
logical conditions either of the liver- or bile-ducts, causing ob- 
struction to the outflow of the bile or a destruction of the red- 
blood corpuscles.* The blood pigments, according to Michaels, 
are easily demonstrable in the desiccated saliva by means of 
polarized light. 

The intestinal juice contains a number of substances play- 
ing an important part in the preparation of food material for 
assimilation. Among them is erepsin (erepase). This is a 
protein-splitting enzyme acting upon the products of tryptic 
digestion. It has little power upon the simple proteins, but will 

* Ogden. 



PANCREATIC DIGESTION AND BILE 339 

split the peptones into amino acids. There are also in the 
intestinal juice certain amylolytic enzymes which continue 
the digestive action started byamylopsin or by ptyalin of the 
saliva. 

Secretin, excreted by the mucous membrane of the intestine, 
is a substance differing materially from the digestive ferments 
in that it is not destroyed by heat. It acts not as an activator 
in the sense that it starts specific chemical action, but as an 
essential constituent for the secretion of the various digestive 
fluids; i.e., the secretin in the blood starts the flow of pancre- 
atic juice, for instance, which contains the parent enzyme, tryp- 
sinogen, which in turn requires the action of enterokinase before 
it is in condition to perform its digestive action. Some authori- 
ties claim that the secretin itself exists as a pro-secretin, from 
which it is liberated by action of acid. 

Laboratory Exercise LXXII. 
Experiments with Pancreatic Juice. 

Exp. 230. Proteolytic Action. — To 25 c.c. of a 1% solution 
of Na 2 C0 3 add a few drops of the pancreatic extract. Place 
some pieces of fibrin in this liquid, and keep in the water-bath 
at 40 C. till the fibrin has disappeared (one or two hours prob- 
ably). Observe the digestion from time to time. Note that 
the fibrin does not swell and dissolve as in gastric digestion, but 
that it is eaten away from the edges. 

Filter. What is the precipitate? Carefully neutralize the 
filtrate with 0.2% HC1. Another precipitate may appear. 
What is this? 

Again filter, if necessary, and test the filtrate for proteoses 
and peptones as directed under gastric digestion. 

Exp. 231. Formation of Leucin and Tyro sin. — Perform a 
similar experiment, using boiled fibrin and adding a few drops 
of a 20% solution of thymol, or a few drops of chloroform water. 



340 DIGESTION 

Why use boiled fibrin, and why add thymol or chloroform? 
Digest for forty-eight hours, and then examine as follows: 
Filter, neutralize, and concentrate by evaporation on the water- 
bath. Crystals of tyrosin (and possibly leucin) usually sepa- 
rate. Examine microscopically. 

Exp. 232. Amylolytic Action. — To some starch paste in a 
test-tube add a drop or two of the pancreatic extract and place 
in the water-bath at 40 C. After a few minutes test for sugar 
and report the result. 

Exp. 233. The Piolytic {Fat- splitting) Action. — For the 
demonstration of this action use natural pancreatic juice, or 
finely divided fresh pancreas, or a recently prepared extract. 

To some perfectly neutral olive-oil, colored faintly blue 
with litmus, add half its volume of the pancreatic extract, 
shake thoroughly, and keep at 40 C. for twenty minutes. 
Record the result. Reserve for next experiment. 

Exp. 234. Emulsifying Action. — To 10 c.c. of a 0.2% solu- 
tion of Na 2 C03 add a few drops of the mixture used in Exp. 233. 
Shake thoroughly, and report the result. Referring to the 
earlier experiments on emulsification (see Fats), explain the 
efficacy of the pancreatic juice in emulsifying fats. 



Laboratory Exercise LXXIII. 
Experiments with Bile. 

Exp. 235. Color. — Note the difference in color between 
human bile and ox bile. Explain. 

Exp. 236. Reaction. — Dilute some bile with four parts of 
water. Immerse a strip of red litmus-paper, then remove and 
wash with water. Note the reaction. 

Exp. 237. Nucleo-albumin. — Dilute bile with twice its 
volume of water, filter if necessary, and add acetic acid. What is 
the precipitate? How distinguished from mucin? 



PANCREATIC DIGESTION AND BILE 341 

Exp. 238. Filter 237 and test the nitrate for proteins. 
Report the result. 

Exp. 239. Separation of Bile Salts. — Mix 20 c.c. of bile 
with animal charcoal to form a thick paste, and evaporate on the 
water-bath to complete dryness. Pulverize the residue in a 
mortar, transfer to a flask, add 25 c.c. of absolute alcohol, and 
heat on the water-bath for half an hour. Filter. To the fil- 
trate add ether till a permanent precipitate forms. Let the 
mixture stand for a day or two, and then filter off the crystalline 
deposit of bile salts. Save the filtrate which contains choles- 
terin. (Plate VII, Fig. 4, page 296.) 

Exp. 240. Bile- pigments. — (a) Gnielin's Test. — Take some 
bile in a wine-glass and underlay with yellow HN0 3 , in the 
manner described in testing saliva for albumin. Notice the 
play of colors, beginning with green and passing through blue, 
violet, and red to yellow, at the junction of the two liquids. 
Explain. 

(b) Iodin Test. — Place 10 c.c. of dilute bile in a test-tube, 
and add slowly two or three cubic centimeters of dilute tincture 
of iodin, so that it forms an upper layer. A bright green ring 
forms at the line of contact. 

Exp. 241. Cholesterin. — Examine under the microscope the 
crystals obtained by the cautious evaporation of the alcohol- 
ether filtrate of Exp. 239. For color reactions refer to demon- 
strations. 

Exp. 242. Action of Bile in Digestion. — (a) Take three 
test-tubes. In one mix 10 c.c. of bile and 2 c.c. of neutral olive- 
oil; in the second, 10 c.c. of bile and 2 c.c. of rancid olive-oil; 
in the third, 10 c.c. of water and 2 c.c. of neutral oil. Shake and 
place in a water-bath at 40 C. for some time. Note the extent 
and the permanency of the emulsion in each case. 

(b) Into each of two funnels fit a filter-paper. Moisten one 
with water and the other with bile, and into each pour an equal 
volume of olive-oil. Set aside for twelve hours (with a beaker 



342 DIGESTION 

under each funnel). Do you notice any difference in the rate 
of nitration? 

(c) Add drop by drop a solution of bile salts to (a) a solution 
of egg-albumin; (b) sl solution of acid-albumin; (c) a solution 
obtained by digesting a bit of fibrin in gastric juice and filtering. 
Explain the results. 



PART VIIL 

URINE. 



CHAPTER XXXVII. 
PHYSICAL PROPERTIES OF URINE. 

Urine is a solution of waste products from the blood. It 
contains, normally, certain coloring matter, urea, uric acid in 
combination with alkaline bases, various organic constituents 
in slight amounts, including, perhaps, albumin and sugar, 
chlorid of sodium, sulphates and phosphates of the alkalis and 
the alkaline earths. Abnormally the urine may contain albumin, 
sugar, uric acid as such, bile, salts of the heavy metals, lead, 
mercury, and arsenic; occasionally albumose, peptones, lac- 
tates, acid lactates, oxalates, carbonates, hippuric acid, also 
organic compounds, resulting from insufficient or imperfect 
oxidations, as amino-acids, leucin, tyrosin, and acetone bodies. 

We are to study the urine, not primarily with a view to the 
diagnosis of renal disease, which is more particularly the prov- 
ince of the physician, but to detect irregularities or deficiencies 
in the body metabolism, and, as far as possible, we are to study 
the methods whereby we may correct and regulate the mal- 
nutrition which lies at the foundation of many diseases of the 
oral cavity. As has been previously stated by the author,* 
if there are diseases of the oral cavity which may have their 
etiology in some systemic derangement not easily apparent, 
and if such diseases are to receive the attention of the dentist, 
he should obtain all possible light on every case, and at present 

* International Dental Journal, January, 1905. 
343 



344 URINE 

a quantitative analysis of the urine is of greater value than 
any other laboratory aid. In examining a sample of urine to 
obtain information as above indicated, it is essential that the 
sample be a portion of the mixed twenty-four-hour quantity, 
and that the total amount of the twenty-four-hour excretion 
be known. In collecting samples for such analysis a conven- 
ient method is to give the patient a one- or two-dram vial, 
nearly filled with water, and containing three or four drops of a 
commercial formaldehyd solution, with instructions to empty 
this into the bottle, or other receptacle, in which the twenty- 
four-hour sample is collected. Formaldehyd if used in this 
amount has no effect on the subsequent analysis and is a sufficient 
preservative. 

Physical Properties. 

Quantity. — The quantity of urine passed in twenty-four 
hours normally is about 1200 to 1400 c.c. for an adult female 
and 100 or 200 c.c. more than this for the male. The amount 
is increased in Bright's disease, in diabetes, and various other 
pathological conditions, also in cold weather when less mois- 
ture is given off from the skin. Normally, the quantity passed 
during twelve day hours, as 8 a.m. to 8 p.m., will exceed the 
amount overnight from 8 p.m. to 8 a.m. In cases of chronic 
interstitial nephritis the twelve-hour night quantity exceeds the 
day, hence it is desirable in collecting a twenty-four-hour sample 
to divide the time as suggested, and measure the amounts 
separately, especially if there is any suspicion of any chronic 
kidney disease. A diminished quantity of urine may indicate 
simply a diminished amount of water taken into the system. 
The urine is diminished pathologically in acute conditions, such 
as fevers, etc., but such samples rarely reach the dental prac- 
titioner. 

Color. — The normal color of the urine is usually given as 
straw color or pale yellow. If lighter than this the color is 
regarded as pale, if darker than normal it is regarded as high. 



PHYSICAL PROPERTIES OF URINE 345 

The urine may also be colored by various abnormal constitu- 
ents; it may be bright red from the presence of blood, or choco- 
late colored with a so-called coffee-ground sediment from de- 
composed-blood coloring matter. It may be brown to yellow, 
bright blue or green, due to the ingestion of various drugs. 
If bile is present in any quantity in the urine it will have a 
dark or smoky appearance, and, upon shaking, the foam will 
have a distinctly yellowish or yellowish-green tint. 

Appearance. — In addition to the colors mentioned above 
urine may sometimes have a smoky appearance, due to the 
presence of hematoporphyrin or iron-free hematin, often found 
in cases of lead-poisoning. It may have a milky appearance, 
due to presence of finely divided fat globules, as in chylous 
urine, due to parasitic disease of the blood. It may be cloudy 
from four principal causes: first, amorphous urates; second, 
amorphous phosphates; third, pus; and fourth, bacteria. 
These may easily be distinguished. The application of a slight 
degree of heat (insufficient to cause coagulation of albumin) 
will redissolve the urates, and clear a urine which is cloudy 
from this cause. A deposit of phosphates is increased by the 
application of heat, but clears easily upon the addition of a 
few drops of acetic acid. A urine cloudy from the presence 
of pus is not cleared by either of these methods, but the cloud 
settles with comparative rapidity and pus corpuscles are easily 
recognized by microscopical examination of the sediment. If 
bacteria are present in sufficient quantity to cause cloudiness, 
the sample is apt to be alkaline in reaction and will not clear 
upon filtering. If it is necessary to obtain a clear solution, a 
little magnesium mixture may be added to the urine, then a 
little sodium phosphate; warm gently with agitation, when 
the precipitated ammonium magnesium phosphate will me- 
chanically carry down the bacteria, and a filtrate may be ob- 
tained which, after acidifying with dilute acetic acid, will be 
suitable for an albumin test. 



346 



URINE 



^O 



Fig. 27. 



Specific Gravity. — The gravity is most conveniently taken 
with a urinometer (Fig. 27). Care should be taken in the selec- 
tion of this instrument so that the scale graduation may be accu- 
rate. The fact that the instrument will sink in distilled water 
at the proper temperature (usually 6o° F., 15^° 
C.) to the o mark, is not a sufficient proof of its 
accuracy, as many cheap instruments will do 
this, and give erroneous readings at the higher 
markings of the scale. Distilled water is rep- 
resented by 1000, and the relative increase in 
the comparative gravity of urines will be easily 
represented on the scale ranging from 1000 to 
1050. As the first two figures of the specific 
gravity are always the same (10), they are 
usually omitted from the scale which is made 
to read from o to 50 or 60. The reading should 
be made, if possible, from underneath the surface of the liquid, as 
the liquid is usually drawn around the stem by adhesion, so that 
accurate readings from the surface are difficult. The specific 
gravity of normal urine is from 1018 to 1022; it decreases in 
cases where the quantity is much above the normal (polyurias), 
unless sugar is present. It is increased by the presence of sugar 
or by concentration, whereby the normal solids are relatively 
increased. In case the quantity of urine is too small for the 
determination of the gravity in the usual way, the urinopyk- 
nometer, devised and recommended by Dr. Saxe in his " Examina- 
tion of the Urine, " may be employed. See page 317, on specific 
gravity of saliva. 

Reaction. — The reaction of urine is normally acid to litmus- 
paper, due to the presence of acid sodium phosphate. The 
degree of acidity is roughly indicated by the intensity of color 
produced with the carefully prepared litmus-paper. More ac- 
curate results may be obtained by a regular volumetric exam- 
ination (with N/20 alkali), or by the test for urinary acidities 



PHYSICAL PROPERTIES OF URINE 347 

given by Freund and Topfer who suggest the following 
method : 

" To 10 c.c. of the urine add two to four drops of a 1% solu- 
tion of alizarin. If the resulting color is pure yellow, free acids 
are present; if deep violet, combined acid salts. If none of 
these colors appear, there are present acid salts of the type 
of disodic phosphate. The amount of one-tenth normal HC1 
standard solution required to produce a pure yellow color repre- 
sents the alkaline salts, while the amount of one- tenth normal 
sodium hydrate required to cause a deep violet represents the 
acid salts/ ' 



CHAPTER XXXVIII. 

NORMAL CONSTITUENTS OF URINE. 

The more important normal constituents of the urine are 
urea, uric acid (combined as urates), chlorids, phosphates, 
sulphates, indoxyl, coloring matters; traces of mucin, organic 
acids, carbonates, hippuric acid, creatin, and creatinin may also 
be present. The total normal solids are composed approxi- 
mately of 50% urea, 25% chlorid of sodium; at least one half 
of the remainder are phosphates and sulphates. We see that 
the constituent which most influences the specific gravity is the 
urea, and in normal samples the specific gravity is an index of 
the amount of urea present. The total solids may be calculated 
by multiplying the last two figures of the specific gravity by 
2 J,* which will give approximately the number of grams of solids 
in one liter of urine; from this the solids in the twenty-four- 
hour amount may be easily calculated. 

Urea. 

The chemistry of urea has been already considered (page 
232). 

Detection. — A qualitative test for this substance is obvi- 
ously superfluous, although such may be made by obtaining 
the crystals of urea nitrate or oxalate (page 233). The quan- 
tity of urea is of great importance, especially in cases where 
there is any question in regard to the body metabolism or the 
amount of nitrogen excreted. By far the greater proportion 
of all nitrogenous waste is eliminated by the kidneys in the 
form of urea, a comparatively slight amount as other nitroge- 

* Coefficient of Haeser. 
348 



NORMAL CONSTITUENTS OF URINE 



349 



nous constituents of the urine, a still smaller amount in the feces, 
and traces only by other avenues. The urea may be quanti- 
tatively determined by various methods, the hypobromite 
method being the most practical. 

Quantitative Determination. — There are various forms of 
apparatus used in connection with this process. 

The one devised by Dr. Squibb is pictured in Fig. 28. It 
has been quite generally used; hence its description is given. 
It is not recommended, because a source of considerable error 




Fig. 28. 



lies in the fact that the gases (C0 2 and N) evolved from the urea 
are very apt to be driven over into bottle A before all the CO2 
has been absorbed by the reagent in B and consequently the 
results are higher than they should be. 

The first step in the use of this apparatus is to completely 
fill the bottle A, including the tubes D and H, with water, 
with the glass plug E closing the lower end of D. Next put 
5 c.c. each of a 40% solution of caustic soda and a bromine 
solution in potassium bromide* into B. Place the stopper in 
B and connect the tube C at H, then fill accurately the 2-c.c. 
pipette with urine. Place in position in the stopper of B 
as shown in the cut, remove E from the rubber tube D, and 



* For preparation of this solution see Appendix. 



35o 



URINE 



allow D to fall to the bottom of the graduate as indicated. 
Pressure is now applied to the bulb of the pipette, so that the 
2 ex. of urine is forced with moderate rapidity into the bottle. 
As the pressure on the bulb is released, water will be drawn 
back into A , and it is essential that the end of D be under water 
during this part of the process. Bottle B should be agitated 
to insure complete decomposition of the urea. Nitrogen and 
carbon dioxid are at once evolved according to the reaction on 
page 233. The 40% solution of caustic soda is strong enough to 
absorb and hold the C0 2 . The nitrogen passes 
into A , forcing a corresponding volume of water 
into the graduate. This volume of gas, read in 
cubic centimeters of the water, will give the 
percentage of urea in the sample examined, 1 c.c. 
of nitrogen being equivalent to 0.126 gram of 
urea. 

The Doremus-Hinds apparatus shown in 
Fig. 29 gives a perfectly satisfactory method 
for the estimation of urea by the hypobromite 
method. The reagent, equal parts of bromin 
solution and 40% NaOH (Appendix, page 380), 
is introduced into R and the tube completely 
filled. The tube U is next filled exactly to the o mark, then by 
means of the stop-cock S 1 c.c. of urine is allowed to enter T 
a few drops at a time and slowly enough to prevent any escape 
of gas through R. The gas rises in small bubbles through a 
comparatively long tube and remains in contact with the reagent 
which insures perfect absorption of C0 2 , thus overcoming the 
greatest objection to the Squibb 's apparatus. 

The tube T is graduated to read centigrams of urea in 1 c.c. 
of urine. 

Uric Acid. 

Uric acid and its antecedents, the xanthin bases, are derived 
from the decomposition of nuclein and nucleoprotein. For 




Fig. 29. 



NORMAL CONSTITUENTS OF URINE 351 

chemistry of this substance, see pages 235 to 237. The uric 
acid is increased by a highly nitrogenous diet and certain vege- 
table substances which contain purin (page 235) derivatives, 
such as coffee, tea, and cocoa. The so-called red meats, beef, 
mutton, etc., are regarded as the most abundant source of uric 
acid and urates. As previously suggested uric acid does not 
occur in normal urine as such, but is combined with the alka- 
line bases. 

Detection. — It is unnecessary to make a qualitative test in 
urine, as urates are always present. If a qualitative test is de- 
sired the murexid test, as given on page 239, is available. Uric 
acid is most conveniently determined quantitatively by the 
centrifugal method as devised by Dr. R. Harvey Cook.* The 
detail of this method is as follows: Measure 10 c.c. of urine into 
a graduated tube, used in the centrifugal machine, add a few 
grains of sodium carbonate, and about 3 c.c. of strong ammo- 
nium hydrate. Place in the centrifuge, and allow to run for one 
or two minutes, then carefully decant the clear urine into another 
graduate tube, leaving the precipitate which consists of earthy 
phosphates. The bulk of this precipitate may be noticed and 
an idea obtained as to whether the earthy phosphates are present 
in normal quantities or not. To the clear urine add 2 or 3 c.c. 
of ammoniacal silver-nitrate solution (AgN0 3 , 5 grams; dis- 
tilled water, 80 c.c; strong ammonia, 20 c.c), and run in the 
centrifuge till the precipitate of silver urate has reached its 
lowest obtainable reading. The ammonia will prevent the pre- 
cipitation of chlorids and, unless iodids or bromids are present, 
the precipitate will be fairly pure silver urate, each tenth of a 
cubic centimeter of the precipitate being equivalent to 0.001176 
gram of uric acid in the 10 c.c. of urine used, or 0.01176%. 

The silver precipitate is by no means pure silver urate, 
many of the other nitrogenous bases in urine forming insoluble 
silver salts. These occur only in very slight traces; so, for 

* Medical Record, Mar. 12, 1898, p. 373. 



352 URINE 

clinical purposes, the method is available unless the sample 
contains bromids or iodids, when iodid or bromid of silver will 
be formed, insoluble in the amount of ammonia usually used. 
More accurate results may be obtained by either Hopkins' or 
Folin's method. These are somewhat similar and consist of pre- 
cipitation of the uric acid as ammonium urate, ioo to 200 c.c. 
of urine is used and the precipitation effected by a saturated 
solution of NH4CI (Hopkins' method) or 10 grams ammonium 
sulphate (Folin's method). 

The precipitate is washed in the reagent and dissolved in 
boiling water and the amount of uric acid determined by titra- 
tion with N/20 permanganate of potassium. Each cubic centi- 
meter of KMn0 4 used is equal to 0.00375 grams of uric acid. 

Ammonia Determination. 

The amount of ammonia normally present in urine is about 
0.7 gram in the 24-hour amount. Ammonia is increased in any 
systemic condition resulting in an increase of acidic elements 
(Acidosis), or upon ingestion of ammonium salts of inorganic 
acids, i.e., salts not easily oxidized to urea. 

Normally, the quantity of NH 3 follows more or less closely 
the urea and the protein metabolism, and amounts to about 
one-half of one per cent or about 0.7 gram in 24 hours. 

Determination may be made as follows: 

Folin's New Method. — Measure by use of standardized 
"Ostwald pipette" 1 or 2 c.c. of urine into a large Jena test- 
tube. Then proceed exactly according to method given for 
saliva on page 320. 

Formaldehyd Method. — Place 10 c.c. urine in a 250 c.c. 
Erlenmeyer flask, add 50 or 60 c.c. H 2 0, titrate with N/10 NaOH 
with phenolphthalein as an indicator. The amount of NaOH 
used will represent total acidity of sample. 

After exact neutralization add 10 c.c. of previously neutra- 
lized commercial formaldehyd solution and titrate again with 



NORMAL CONSTITUENTS OF URINE 353 

N/10 NaOH. The second amount of alkali added represents 

ammonia as follows: 

4 NH4CI + 6 CH 2 + 4 NaOH = N 4 (CH 2 ) 6 + 10 H 2 + 4 NaCl. 

As the ammonium salts and the caustic soda react molecule 
for molecule it is possible to make calculation for quantity of 
NH 3 by multiplying the N/10 factor (0.0017) by the number of 
cubic centimeters of N/10 NaOH used. 

In cases of diabetes when the ammonia reaches a compara- 
tively large amount the figures obtained by this process will be 
found to be a little high, as amino-acids are also acted upon by 
the NaOH, and will be calculated as ammonia, but for ordinary 
work or clinical comparisons this method is very simple and 
sufficiently accurate. 

This method is not affected by urea, uric acid, creatin, 
creatinin, purin bases or hippuric acid.* 

Chlorids. 

The chlorids are represented in the urine chiefly by sodium 
chlorid. This is present to the extent of from 12 to 20 grams in 
twenty-four hours. An increase above this quantity is unusual, 
although it simply indicates an increase in the ingested salt, 
and is without clinical significance. The chlorin is diminished 
in dropsy, acute stages of pneumonia, and in fevers generally. 

Detection. — The usual qualitative test with silver nitrate and 
nitric acid is employed for detection of chlorid in the urine. 
If one drop of a strong solution of silver nitrate (1 to 8) is 
allowed to fall into the wine-glass in which the albumin test 
has been made (q. v.), the appearance of the resulting precipi- 
tate will give a rough idea of the quantity of chlorin present. 
If a solid ball of silver chlorid is formed which does not become 

* Dr. Hans Malfatti in Zeit. fur Anal. Chemie, 47, page 273. 
Note. — See also the Vacuum Distillation Method, giving very exact results 
when properly carried out: 

H. Bjorn Andersen und Marius Lauritzen, Zeit. fur Physiol. Chemie, 64, 
page 21. 



354 URINE 

diffused upon gently agitating the contents of the glass, the 
chlorin is normal or increased. If the precipitate falls as a 
cloud distributed throughout the liquid, the chlorin is dimin- 
ished. The chlorin may be determined by precipitation with 
silver nitrate in 10 c.c. of urine, and the precipitate settled in a 
centrifuge-tube to constant reading, but this method is not 
recommended, as the precipitate is a bulky one, and usually 
takes a long time for thorough settling. The titration with 
silver nitrate, using potassium chromate as an indicator, really 
takes less time, and is much more accurate. This titration is 
made in the usual way (see page 149), except that, inasmuch as 
phosphates and urates are also precipitated, from three-tenths to 
1 c.c. may be deducted from the amount of the silver-nitrate 
solution used according as it is much or little, thus allowing 
for these substances. An accurate titration of chlorin may be 
made by acidifying the urine with nitric acid, adding an excess 
of standard silver-nitrate solution, and titrating back with a 
standardized sulphocyanate solution (preferably of the same 
strength as the AgN0 3 solution), using ferric sulphate as an 
indicator. But, as a rule, the simpler method gives results 
which for clinical purposes are equally valuable with those of 
this more tedious though more accurate process. 

Phosphates. 

The phosphates in the urine are of two kinds, the alkaline 
phosphates, Na 2 HP0 4 and NaH 2 P0 4 , etc., and the earthy phos- 
phates represented by the magnesium and the calcium phosphates. 
The phosphates are normally present to the extent of two and a 
half to three and a half grams, calculated as P 2 5 (in twenty-four 
hours) . 

The triple phosphates, ammonium magnesium phosphates 
(Plate IV, Fig. 2, p. 163), are the forms in which phosphoric acid 
is usually found in urinary sediment. Crystals of acid calcium 
phosphate are occasionally found, and resemble the acid sodium 



NORMAL CONSTITUENTS OF URINE 355 

urate in form (Plate X, Fig. 3, p. 368), except that they are 
usually a little broader and more often occur in fan-shaped 
clusters. They may be distinguished by treatment with acetic 
acid, which dissolves the calcium phosphate promptly, while the 
urate is slowly dissolved and crystals of uric acid appear after 
a little time. The phosphates are deposited from neutral or 
alkaline urines and when this precipitation takes place within 
the body, the crystals cause more or less irritation to the urinary 
tract and may form aggregations which result in calculi. Phos- 
phates are supplied by either a cereal or meat diet. They may 
be much increased in diseases accompanied by nervous waste, 
or by softening and absorption of bone. Phosphates are dimin- 
ished in gout, in chronic diseases of the kidney, and during 
pregnancy. 

Detection. — A qualitative test for earthy phosphates 
(E.P.) may be made by taking a test-tube half-full of urine, and 
making alkaline with ammonium hydrate. When the precipi- 
tate has thoroughly settled, if it is about 1/4 to 1/2 inch in 
depth, it represents normal, earthy phosphates. If this mixture 
is now filtered, the alkaline phosphates (A. P.) may be deter- 
mined in the filtrate by the addition to the solution of one-third 
its volume of magnesium mixture.* The precipitate after 
settling will be 1/2 to 3/4 of an inch in depth if normal. The 
total phosphates may be determined in the centrifugal machine 
by adding 5 c.c. of magnesium mixture to 10 c.c. of urine. Each 
tenth of a cubic centimeter of the centrifugalized sediment will be 
equivalent to 0.0225 of P2O5. 

A more accurate determination of the total phosphoric acid 
may be made by the titration with uranium nitrate or acetate 
solution as follows : 

Reagent Required. — First. A standard solution of uranium 
nitrate or acetate made by dissolving 35.5 grains of pure salt 
(the molecular weights of the two salts differ so little that the 

* See Appendix. 



356 URINE 

same weight of either may be used) in sufficient water to make 
iooo c.c. 

Second. A sodium acetate solution containing ioo c.c. 
of 30% acetic acid and 100 grams of sodium acetate in enough 
distilled water to make 1000 c.c. 

Third. An indicator consisting of a saturated solution of 
potassium ferrocyanid. 

Process. — Place 50 c.c. of urine with 5 c.c. of sodium 
acetate solution above described in a small Erlenmeyer flask 
and heat nearly to the boiling-point. Titrate, while hot (8o° 
or above), with the standard uranium solution till a drop of the 
mixture placed on a white porcelain tile with a drop of the indi- 
cator (K 4 FeCy 6 ) gives a distinct brown color. This method of 
determining the end point is known as " spotting" and with a 
little practice gives very accurate results. 

The number of cubic centimeters of uranium solution multi- 
plied by 0.01 will give the weight of P 2 5 in 100 c.c. of urine 
(1 c.c. of reagent being equal to 0.005 gram P 2 5 ). 

Sulphates. 

The sulphates in the urine are present as alkaline sulphates, 
K2SO4 and Na 2 S0 4 ; also as ethereal sulphates, represented by 
such compounds as indoxyl potassium sulphate, page 250. 

Detection and Determination. — The sulphates may be de- 
tected by precipitation with barium chlorid in HO solution. If 
the precipitate is obtained from 10 c.c. of urine and centrifugal- 
ized to constant reading, the per cent of sulphuric acid by weight 
will be one fourth of the volume per cent of the precipitate. 
The sulphates follow rather closely the urea, and their determi- 
nation is not of great importance. They are increased in acute 
fevers, dimimshed in chronic diseases generally, and markedly 
diminished in carbolic-acid poisoning. (Ogden.) 

Coloring Matter. — Urobilin, an important coloring matter 
of the urine, exists as a parent substance or chromogen to which 



NORMAL CONSTITUENTS OF URINE 357 

has been given the name urobilinogen. This undergoes decom- 
position by action of light with liberation of urobilin. 

Urobilin is without doubt derived from the bilerubin of the 
bile, which, in turn, comes from the hemochromogen of the blood. 
Dr. J. B. Ogden is authority for the statement that "it is safe 
to infer that the amount of urobilin in the urine is a measure of 
the destruction of the hemoglobin or blood pigment. " 

Urochrome is a pigment to which the yellow color of urine 
is chiefly due. Uroerythrin and urorosein are less important, 
existing only in very slight quantities, but they are responsible 
for colors of some sediments and of decomposition products 
which are noticed in analysis. 

Indoxyl. 

The indoxyl is of considerable importance, as an increase 
above the normal amount is indicative of increased putrefaction 
of nitrogenous substances taking place in the small intestine. 
Indoxyl may also be increased by acute inflammatory process 
of the peritoneal cavity. Ordinary constipation does not in- 
crease the indoxyl. The test for indoxyl depends upon the 
oxidation of the indoxyl potassium sulphate to indigo blue 
according to the following reaction : 

2 C 8 H 6 NKS0 4 + 2 = 2 C 8 H 5 NO + 2 KHS0 4 . 

Indoxyl potassium sulphate. Indigo. 

Detection and Determination. — 15 c.c. of strong HC1 is 
placed in a wine-glass, and a single drop of concentrated nitric 
acid added; then 30 drops of urine are stirred into the mixture. 
If indoxyl is present, an amethyst color develops in from five to 
fifteen minutes. If the color is purple, the indoxyl is increased. 
Variation of the amount of indoxyl within normal limits is 
rather wide, and the indoxyl may be reported as high or low 
normal, increased, or diminished. 



CHAPTER XXXIX. 
ABNORMAL CONSTITUENTS OF URINE. 

The principal abnormal constituents are albumin, sugar, 
acetone, bile, and various crystalline salts, discoverable either 
by microscopical examination of the sediment, or by evapora- 
tion of a clear fluid, and examination with the micropolari- 
scope. 

Metallic substances, arsenic, lead, and mercury are occa- 
sionally present, and tests should be made for them when gen- 
eral symptoms or the conditions of the kidney indicate metallic 
poison. Albumin is probably present in minute traces in the 
majority of urines. When in sufficient quantity to be detected 
by the usual laboratory methods, it is essential that we learn 
the source from which it has been derived, for the simple pres- 
ence of even a considerable trace of albumin may be of but 
slight clinical importance. Albumin may indicate either a 
pathological condition of the kidney, which allows the entrance 
into the renal tubules of serum-albumin from the blood, or it may 
indicate a change in the composition of the blood, whereby the 
albumin passes more easily through the renal membranes, or its 
presence may be due to irritations from various sources of the 
urinary tract; and, as regards the bearing of albuminurias on 
dental disease, it is sufficient simply to determine whether renal 
disturbance is primary or secondary to some other trouble, such 
as heart disease; or purely local, as when caused by irritation due 
to crystalline elements. 

Detection. — Albumin may be detected by either of two 
simple methods. It is often desirable to use both of these 
methods, thereby eliminating possible confusion from the 

358 



ABNORMAL CONSTITUENTS OF URINE 



359 



presence of substances other than albumin, which may respond 
to one of the two tests, but not to both. 

The first consists simply in underlaying about 25 c.c. of 
filtered urine in a wine-glass with concentrated nitric acid. 
The wine-glass should be tipped as far as possible and the acid 
allowed to run very slowly down the side. This method is pref- 
erable to the use of the apparatus known as the albuminoscope 
or Horismascope (Fig. 30). As this latter method does not 





Fig. 30. 



Fig. 31. 



provide for sufficient mixing of nitric acid with the sample, the 
albumin is shown by a narrow white ring at the plane of contact 
of the two liquids. A white ring above the plane of contact is 
not albumin, but is composed of acid urates, indicating an excess 
of urates in the sample (Fig. 31). The albumin, in distinction 
from this band, occurs directly above the acid and is usually 
reported as the slightest possible trace when just discernible; 
as a slight trace, when well marked, but not dense enough to 
be seen by looking through the liquid from above; as a trace, 
when the white cloud may be seen by looking down into the 
glass from above and a large trace if plainly visible in this way. 
Acetic acid and heat method of testing for albumin is the 
other method referred to in the preceding paragraph. It is of 
about the same delicacy as the nitric acid test, and is less liable 
to respond to substances other than albumin. It is made as 
follows : 




360 URINE 

A test-tube is filled two thirds full of perfectly clear filtered 
urine, one drop of acetic acid added and the upper half of the 
sample boiled. The tube can easily be held in the hand by the 
lower end. After boiling, if the tube is examined before a black 
background, a slight cloudiness or turbidity resulting from 
coagulated albumin can be easily detected in the upper part of 
tube. Anything more than a trace should be ' determined in 
the centrifugal machine by mixing 10 c.c. of filtered urine 
with about 2 c.c. of acetic acid and 3 c.c. of potassium 
ferrocyanid solution. Each tenth of a cubic centimeter 
of the precipitated albumin, when settled to constant 
reading, indicates one sixtieth of one per cent albumin 
by weight. This factor is fairly correct up to four or 
five tenths of a cubic centimeter of precipitate; beyond 
this it is of little value, and the albumin is best deter- 
mined quantitatively by measuring 50 or 100 c.c. of 
urine into a small beaker, adding a drop of acetic acid, 
and boiling, which will completely precipitate the al- 
bumin. It may then be filtered into a counterpoised 
filter, thoroughly washed, first in water, next in alcohol, 
and lastly in ether, dried at a temperature a little 
' below the boiling-point of water, and weighed. Esbach's 
method may be of value in some instances, and is carried out 
as follows: 

Fill the albuminometer (Fig. 32) with urine to the line U, 
and then add the reagent* to the fine R; close the tube, mix the 
contents thoroughly, and allow to stand in an upright position 
for twenty-four hours. At the end of that time the depth of 
precipitate may be read by the figures on the lower part of the 
tube, these figures representing tenths of one per cent of albu- 
min, or grams of albumin in a liter of urine. If a sample of 
urine contains more albumin than is easily estimated by the 

* Esbach's reagent consists of picric acid, 10 grams; citric acid, 20 grams, and 
distilled water sufficient to make one liter. 



ABNORMAL CONSTITUENTS OF URINE 361 

centrifugal or Esbach's method, approximate results will be 
obtained by diluting with several volumes of distilled water, 
until the quantity of albumin precipitated is within the limit 
of the test. The proteoses occasionally occur in the urine, and 
are distinguished from albumin by the fact that they redissolve 
at a boiling temperature. If filtered while hot, albumin, which 
usually accompanies them, will remain on the paper, while 
albumose will separate out from the clear nitrate as it cools. 

Sugar. 

Sugar in urine represents a perverted process of oxidation 
for which the liver is largely responsible. The pancreas also 
often plays an important part in cases of diabetes, but just 
how this is done is not clearly known. Sugar in the urine 
does not of necessity indicate diabetes any more than albumin 
indicates Bright's disease. Many cases of glycosuria are of a 
temporary nature and respond readily to dietary treatment. 
Whenever sugar is found it is desirable to make tests upon both a 
fasting and an after-meal sample, such as might be obtained 
before breakfast and one hour after dinner. If the fasting sample 
is comparatively free from sugar, it indicates that the glycosuria 
is of a temporary nature and due to faulty metabolism, rather 
than to any organic disease of the liver or pancreas. 

Detection. — Sugar in the urine may be detected by several 
general carbohydrate tests, as previously given. The one which 
is most valuable and most generally employed is Fehling's 
test (Exp. 136, page 262). It is best to modify this test by 
bringing the Fehling's solution to active ebullition, adding from 
5 to 30 drops of the suspected sample and allowing to stand 
without further heating. This prevents possible reduction of 
the sugar by xanthin bases or other occasional constituents of 
the urine, which might give misleading results if the mixture 
were boiled after addition of the sample. There is less danger 
of trouble of this sort if the gravity of the urine is below normal. 



362 URINE 

If it is necessary to make a rapid test, the mixture may be boiled 
after the urine is added, and in case the result is negative there 
is no need of further test; if, however, a slight reduction of the 
copper solution takes place, it will be necessary to repeat the 
test, using the precaution above given. The fermentation test 
(Exp. 140, page 262) may also be used to detect the presence of 
sugar and, approximately, the amount. The phenyl-hydrazine 
test may be used as a confirmatory test or in cases where very 
minute quantities are suspected. This test is considered about 
ten times as delicate as the Fehling's test; consequently, it may 
show small amounts of sugar which are not detected by the 
more rapid process. Quantitatively, sugar may be determined 
by the use of Fehling's solution as follows: 

If the urine contains more than a trace of albumin, this 
substance should be removed by adding a drop of acetic acid 
and heating; after filtration the sample should be cooled and 
restored to original volume with distilled water. If specific 
gravity of the urine is more than 1025, it should be diluted to 
ten times its volume with distilled water (urine, one part; water, 
nine). If the gravity is less than 1025 dilute it to five times its 
volume, mix, and fill a 25 c.c. burette. In a 250 c.c. flask place 
10 c.c. each of the alkaline tartrate and copper sulphate solu- 
tions (Fehling's solution), and add about 100 c.c. of distilled 
water. Place the flask over a Bunsen burner, and bring to a 
boil. If no change takes place after a minute or two of boiling, 
add the solution from the burette gradually, until the precipitate 
becomes sufficiently dense to obscure the blue color of the solu- 
tion. Continue to boil for one or two minutes, then remove 
from the flame and watch carefully the fine directly beneath 
the surface of the liquid, which will appear blue until all of 
the copper has been reduced to the red suboxid. The solution 
should be kept at the boiling-point throughout the entire oper- 
ation, except in making the examination of the meniscus between 
the additions of the diluted urine. These additions must be 



ABNORMAL CONSTITUENTS OF URINE 363 

made very carefully, and as the process nears completion not 
more than one or two drops should be added at a time. When 
the blue color has entirely disappeared, and the line of meniscus 
has become colorless, note the number of cubic centimeters of 
dilute urine used, and calculate that in that quantity there is an 
equivalent of 0.05 gram of glucose; in other words, 0.05 gram 
of glucose will exactly reduce the amount of Fehling's solution 
used, and from this fact the amount of glucose in the entire 
twenty-four hour amount of urine is easily calculated. If the 
titration is carried beyond the proper "end point" the meniscus 
will appear yellow instead of colorless. 

The fermentation test for sugar is a convenient and easily 
made qualitative test, it being only necessary to fill a fermen- 
tation tube (Fig. 17, page 263) absolutely full of urine to which 
a small portion of yeast has been added, and to allow the tube 
to stand in a warm place for several hours. Any collection of 
gas in the top of the tube will indicate the presence of sugar. 
This method may also be used as a quantitative test for sugar 
by taking two portions of the same sample, adding yeast to 
one, and using the other as a control. At the end of twenty- 
four hours, C0 2 is removed from fermented sample, the specific 
gravity of both samples is carefully taken, and the loss of 
density in the fermented sample is calculated as sugar by multi- 
plying the number of degrees lost in gravity by 0.23, water 
being considered as 1000. 

The optical analysis for sugar may be made with a polariscope, 
preferably constructed for use on urine. This determination 
depends upon the ability of glucose to rotate the plane of polar- 
ized light toward the right, the degree of rotation indicating 
the amount of sugar in a pure solution. Of course, allowance 
or correction must always be made for the presence of any sub- 
stances which will rotate the light in the opposite direction,, 
such as albumin, laevulose and fi oxybutyric acid. 

For the detail of construction and use of the polariscope^ 



364 URINE 

the student is referred to the more complete works on urine 
analysis by Ogden, Holland, or Purdy. 

Acetone. 

Acetone may occur in the urine as a result of various patho- 
logical conditions and according to von Noorden they are all 
due to some one-sided perversion of nutrition. The aceto- 
nurias attendant on diabetes, scarlet fever, pneumonia, small- 
pox, etc., are of less practical interest to the dental practitioner 
than those more often overlooked by the medical profession, 
and which indicate improper diet, possibly resulting in serious 
malnutrition. The following points may be noted: In ad- 
vanced stages of diabetes, acetone appears in the urine accom- 
panied by diacetic acid. An increased ingestion of proteins 
may result in the appearance of acetone, in which case the direct 
cause is more an "insufficient utilization of carbohydrates"* 
than the increase of protein. Acetone may result from the oxi- 
dation of jS oxybutyric acid. Diacetic acid is first formed, and 
subsequently the carboxyl group is replaced by an atom of 
hydrogen, as shown by the following graphic formulae: 

j8 oxybutyric acid: CH 3 -CHOH-CH 2 -COOH. 
Diacetic acid: CH 3 -CO-CH 2 -COOH. 
Acetone: CH3-CO-CH3. 

Detection. — Acetone may be detected in the urine by the 
production of iodoform, as described under analysis of saliva 
on page 321, but it is not in this case nearly so delicate a test 
on account of the odor and acid character of the urine. A 
more useful test is known as Legal's test and is made as follows: 
To a third of a test-tubeful of urine add a few drops of a freshly 
prepared and fairly concentrated solution of sodium nitro- 
prussid, next add two or three drops of strong acetic acid, and 
then a considerable excess of ammonia. If the contents of the 

* Von Noorden's Diseases of Metabolism and Nutrition. 



ABNORMAL CONSTITUENTS OF URINE 365 

tube are mixed by a rather rapid rotary motion without invert- 
ing or violent shaking, the ammonia will not reach the bottom 
of the tube, and the presence of acetone will be indicated by a 
violet-red band above the layer of acid liquid. If much acetone 
is present a deep violet to purple color is obtained. 

Diacetic Acid occasionally occurs in urine as an abnormal 
constituent most commonly in advanced stages of diabetes, 
usually accompanied by acetone and /3 oxybutyric acid. It 
may be detected by adding to the urine a little ferric chlorid, 
when a dark wine red color is produced. If a precipitate of 
ferric phosphate is obtained, filter the urine and examine the 
nitrate for color. This test may be made fairly distinctive for 
diacetic acid by boiling and cooling a second portion of the 
urine previous to making the test, when the result will be nega- 
tive if the color at first produced was due to diacetic acid. 

Bile. 

Bile may occur in the urine as such, due to pathologic con- 
ditions of the liver- or bile-ducts, as stated on page 338. The 
coloring matters of the bile may also occur from causes aside 
from lesions of the liver. A urine containing bile or bile-pig- 
ments is always more or less highly colored, and upon shaking 
the foam will be of a yellow or greenish-yellow color. Albumin 
and high indoxyl accompany the presence of bile and there is 
also usually considerable renal disturbance. It may be detected 
by carefully adding to one-half a wine-glass of the suspected 
sample a few cubic centimeters of the alcoholic solution of iodin 
(tincture of iodin) . A green color will be observed just beneath 
the line of contact of the two liquids (page 341). The test may 
be conveniently made by placing the iodin first in the wine-glass 
and then with a pipette introducing the urine beneath the iodin 
solution. 



366 URINE 

Metallic Substances. 

Arsenic, mercury, and lead are the three metals which it 
may be necessary to look for in a sample of urine. The method 
for the detection of mercury, given on page 330, is applicable 
for this purpose. 

Arsenic may be detected by the Marsh-Berzelius test (page 
29), after oxidizing all organic matter. The process may be 
carried out as follows: Evaporate to dryness a liter of urine, 
to which 200 c.c. of strong nitric acid has been added; add to 
the residue, while still hot, from 15 to 20 c.c. of concentrated sul- 
phuric acid. This must be done in a large porcelain evaporat- 
ing-dish, or else the acid must be added very slowly to prevent 
frothing over and loss of a portion of the sample. After the 
action has quieted down the whole mixture may be trans- 
ferred to a 500 c.c. Kjeldahl flask and heat applied gradually at 
first, and then more strongly. It will be necessary to add from 
time to time small portions of nitric acid and possibly a little 
more sulphuric acid; as the oxidation progresses the liquid in the 
flask becomes lighter in color and at the completion of the process 
is water- white, even when the temperature is increased so that 
sulphuric-acid fumes are given off. After cooling, the strongly 
acid liquid is diluted with four or five times its volume of water, 
filtered, if necessary, to remove excessive amounts of earthy sul- 
phates, and is then ready for the arsenic test. 

Lead. — The sample of urine to be tested for lead should 
measure at least 1000 c.c, and should be tested for iodin to 
insure the fact that the patient has been under treatment with 
potassium iodid to dissolve lead salts, otherwise a negative 
result may be obtained when lead is actually present and poison- 
ing the system. Oxidize the sample in precisely the same manner 
as when making the arsenic test, up to the point of diluting the 
strong acid solution with water; then, in this case, use rather less 
water for the dilution, allow to cool, and neutralize with Squibb's 



ABNORMAL CONSTITUENTS OF URINE 367 

ammonia, acidify quite strongly with acetic acid, and pass H 2 S 
gas into the solution. It is desirable to leave the solution satu- 
rated with H 2 S for at least twelve hours. Then filter, and with- 
out washing dissolve the precipitate in warm dilute nitric acid, 
evaporate the HN0 3 solution to dryness, add 5 c.c. of water, 
make alkaline with a drop or two of ammonia, and again acidify 
with acetic acid and add a solution of bichromate of potash.* 
Allow to stand several hours, filter off the chromate of lead, wash 
several times with distilled water, and lastly with H 2 S water 
when the lead chromate will blacken from the formation of lead 
sulphid. This stain is a superficial one and disappears upon 
standing, but when the process is conducted in this way it con- 
stitutes a very delicate and satisfactory test for lead in either 
urine or saliva. 

Urinary Sediments. 
The sediment which settles from a sample of urine upon 
standing consists normally of a slight amount of mucin and 
epithelial cells. It may contain also bacteria and a consider- 
able variety of extraneous matter, including starch grains, 
various vegetable spores, yeast cells, fibers from various fabrics, 
cotton, wool, flax from linen, etc., diatoms, scales from insects' 
wings, and other particles which may occur as dust (see Plate 
IX, Fig. 6; also Plate X, Fig. 4). Under abnormal conditions 
the sediment may contain crystalline elements, including uric 
acid and urates, phosphates, oxalates, cystin, tyrosin, leucin, etc., 
also organized elements such as epithelium, renal or other casts 
(Plate IX, Fig. 4), blood globules, pus cells (Plate IX, Fig. 3), 
spermatozoa (Plate IX, Fig. 2), fat, mucin (Plate IX, Fig. 5), etc. 
Urinary sediment may be thrown down from a fresh specimen 
by the use of the centrifugal machine, or it may be allowed to 
stand in a glass tube with rounded bottom for several hours, when 
the sediment settles to the bottom by gravity. If possible 

* Natural chromate of potash will precipitate copper, the acid chromate 
precipitates lead only of the second group metals. 



368 URINE 

it is best to examine sediments settled in both of these ways, 
as the centrifuge will show elements, such as small casts, that 
would settle slowly, possibly not at all, by the gravity method. 
On the other hand, the sediment allowed to settle spontane- 
ously will often give a more correct idea of comparative num- 
bers of the various elements observed, than when settled in a 
centrifuge-tube. A drop or two of formalin may be used to 
preserve urinary sediment, as suggested on page 344, but if too 
much of this substance is used, especially in urines containing 
high percentages of urea, a compound is liable to be formed which 
has been called formaldehydurea (Plate X, Fig. 5), which settles 
with the sediment and seriously interferes with the micro- 
scopical examination. This compound may form sheaf -like 
crystals similar to tyrosin and may be mistaken for crystals of 
sodium oxalate, especially when examined with a low power 
objective. 

Uric Acid. — Uric acid is deposited from normal urine, upon 
standing, with an excess of free acid (HC1). Urines that have 
a high degree of acidity will also produce a like deposit, and the 
finding of uric-acid crystals does not necessarily signify that 
the crystallization took place within the body, unless special 
care has been taken that the sample examined was perfectly 
fresh, although the tendency to deposit uric acid is, of course, 
indicated. The urine from which uric acid separates, as such, 
is usually rather concentrated and of strong acid reaction. 
These crystals vary in appearance (Plate X, Figs. 1 and 2), 
but are almost always colored yellow to red. Colorless crystals 
are sometimes observed. They are usually quite small, but of 
the peculiar whetstone shape in which this acid most usually 
crystallizes. The presence of uric acid has practically no effect 
upon the acidity of the sample; for, if the acid separates in a 
crystalline form, it is insoluble, and if it does not separate it is 
in combination as urates, possibly, of course, as acid urates. 
Uric acid exists normally in proportion to urea as about 1 to 50, 



PLATE IX. — URINE. 




Fig. i. 

Ammonium Acid Urate. 




Fig. 3. — Pus. 
A, After addition of Acetic Acid. 





Fig. 2. 
Spermatozoa. 




Fig. 4. 
Renal Casts. 




Fig. 5- 
False Casts and Mucin. 



Fig. 6. 
A, Lycopodium; B, Moth-scales; C, Cork; 
D, Cotton-fibres; E, Wool-fibres. 






ABNORMAL CONSTITUENTS OF URINE 369 

but there is no necessary relationship between the quantities 
of the two substances, and the one may be diminished while 
the other is increased. 

Urates. — Urates may occur as crystalline or amorphous pre- 
cipitates. The crystalline urates are urate of sodium rarely, acid 
urate of sodium (Plate X, Fig. 3, p. 368), and acid ammonium 
urate (Plate IX, Fig. 1, p. 367). The amorphous urates are of the 
alkaline bases, usually sodium, and are frequently precipitated 
by lowering of the temperature after the sample has been passed, 
in such cases the urine assumes a cloudy appearance which is 
cleared up by the application of heat. A sediment consisting 
of urates is usually of a pinkish color. 

Phosphates. — Phosphates in the urinary sediment may be 
amorphous or crystalline. They are of the alkaline earths 
rather than of the alkaline metals, as the latter are soluble in 
both the acid and neutral forms. The amorphous phosphates 
deposit with the change of reaction from acid to alkaline, and 
usually in the form of a so-called triple phosphate of ammonia 
and magnesia (Plate IV, Fig. 2, p. 163). This salt crystallizes in 
two forms. The prismatic form is the ultimate form; that is, if 
the crystallization takes place very slowly, the prismatic form is 
the one in which the salt is thrown out. If it takes place rapidly 
it may be precipitated in the feathery form, but this slowly 
changes over to the prismatic form. The acid phosphates may 
be precipitated closely resembling in appearance the acid urates 
(Plate X, Fig. 3), but may be distinguished from them by their 
ready solubility in acetic acid and failure to produce, after solu- 
tion in acetic acid, any crystals of uric acid such as are obtained 
from the urates. 

Acid Lactates. — These are soluble salts, and are found in 
urine only by evaporation of a drop of the clear fluid and an 
examination of the residue by polarized light. When found in 
the urine, the significance is quite different from that when found 
in the saliva, as in the urine they may possibly be formed from 



370 URINE 

lactates, which indicate a faulty action of the liver, and of course 
they have no connection with tooth erosion. The lactates fur- 
nish evidence of similar character. 

Oxalates. — Oxalates if found in the sediment usually occur 
as calcium oxalates. These crystals assume a variety of forms, 
as shown in Plate II, Fig. i, p. 162. Sodium oxalate (Plate II, 
Fig. 4) may occur in the urine (not, however, in the sediment) , 
and is detected only by evaporating a drop of the clear liquid 
and examining with polarized light. Dr. Kirk claims that an 
oxaluria may be in this way detected for a considerable time 
before the appearance of the oxalate of lime crystals, and hence 
such examination becomes a valuable aid to diagnosis. 

Cystin. — Cystin occurs as six-sided plates. It is a com- 
paratively rare crystal, and indicates insufficient oxidation, par- 
ticularly of the organic sulphur compounds. 

Epithelium. — Epithelium occurs in the urinary sediment 
from any part of the urinary tract. In the male urine it is 
much easier to determine the character of the epithelium than 
in the female, as in the latter the comparatively large amount 
of mucous surface, from which epithelium may be gathered, 
furnishes a great variety of forms which are, of course, without 
clinical significance. The epithelium from the vagina may be 
quite readily distinguished as very large cells with small nuclei, 
lying usually in masses overlapping one another but with com- 
paratively slight density. Renal epithelium may be found as 
small, round cells, differing but slightly in size from a leucocyte. 
They may be a little larger, a little smaller, or about the same 
size. They are round and more or less granular in appearance. 
Epithelium from the bladder varies considerably, but the 
majority of cells would properly come under the general head 
of squamous epithelium, rather large and flat with a distinct 
nucleus of medium size. Epithelial cells from the neck of the 
bladder in male urine are quite typical, being round and com- 
paratively dense with a prominent nucleus. They are four 



PLATE X.— URINE. 




Fig. i. 
Uric Acid. 




Fig. 3. 
A f Sodium Urate; B, Sodium Acid Urate. 





Fig. 2. 
Uric Acid. 




Fig. 4. 
Yeast Cells and Molds. 



Fig. 5. 
Formaldehyd Urea (P. L.). 




ABNORMAL CONSTITUENTS OF URINE 37 1 

or five times the size of a leucocyte and, in cases of irritation 
at the neck of the bladder, are usually present in considerable 
numbers and of quite uniform appearance. 

Renal casts consist of molds formed within the tubules of 
the kidneys which retain the form of the tubules after expul- 
sion into the bladder. According to Ogden the most probable 
theory of their formation is " that they are composed of coagu- 
lable elements of blood that have transuded into the renal tubules, 
through pathologic lesions of the latter, and have there solidified 
to be later voided with the urine, as molds of the tubules." 
Casts are termed blood casts, pus casts, epithelial or fat casts 
according as these elements may adhere with more or less pro- 
fusion to the cast itself. Pure hyaline casts are pale, perfectly 
transparent cylinders, with at least one rounded end which 
can be plainly seen, and may occur occasionally in urine from 
perfectly healthy individuals. Fibrinous casts are highly refrac- 
tive and when seen by white light are of a yellowish color and 
indicate acute renal disturbance. Waxy casts resemble the 
so-called fibrinous as regards density, but they have no color, 
and usually indicate advanced and serious stages of kidney 
disease, while the presence of fibrinous casts has no necessarily 
serious significance. 

Blood and Pus are readily recognized under the micro- 
scope after a very little practice. The blood disks are circular 
and show a characteristic biconcavity in the alternate shading 
of the edge and center by slight changes of focus. The red 
corpuscles usually show a shade of color by white light. The 
pus corpuscles or leucocytes are larger than the red corpuscles, 
and are granular in appearance. Treatment with acetic acid 
destroys the granular matter and brings into prominence the 
cell nuclei, two or three in number. If the leucocytes are free 
and scattered they should not be regarded as pus but be reported 
simply as an excess of leucocytes; if they are very numerous and 
occur in clumps they constitute pus. 



372 URINE 

Spermatozoa. — Occasional spermatozoa may be found in 
sediment from either male or female urine and are without clin- 
ical significance. If persistent and in considerable numbers, 
seminal weakness is indicated (Plate IX, Fig. 2, p. 367). 

Fat occurs in urinary sediment as small globules, highly 
refractive and varying greatly in size. They are frequently 
adherent to cells or to casts. Fatty casts indicate a fatty de- 
generation, which may or may not result from chronic disease. 
Fat may be demonstrated by staining with osmic acid which 
is reduced by the double-bonded fatty constituent (olein), 
leaving a black deposit which stains the globule. 

Mucin appears in the sediment as long and more or less 
indistinct threads. An excessive amount usually indicates irrita- 
tion of some mucous surface. The source would have to be 
determined by other more characteristic elements (Plate IX, 

Fig. 5)- 

The salts which may be obtained by evaporation of a drop 
of clear urine and detected by the micropolariscope are simi- 
lar to those occurring in the saliva; sodium oxalate is prob- 
ably most frequently found. If the gravity is above normal 
the urea often crystallizes, making it somewhat difficult to 
pick out the abnormal crystalline constituents. Phosphates 
are also usually observed, but these crystals are large and as a 
rule prismatic, not easily mistaken for anything else. 

Interpretation of Results. 

As stated at the beginning of the chapter on urine, our object 
has been the study of this secretion from the standpoint of gen- 
eral metabolism, rather than with a view to differentiate various 
forms of renal disease, and while it is important that the presence 
of renal disease should be recognized, its further investigation 
constitutes a proper study for the physician rather than for 
the dentist, and when such conditions are found to exist a 
patient's physician should be apprised of the fact. 



Per cent. 


Grams in 
24 hours. 


Urea 0.88 


17.6 


Uric Ac. 0.034 


0.68 


Ammon. 




Chlor. 0.455 


9.1 


Phos. Ac. 0.09 


1.8 


Sugar = abs. 




Uric Ac. to Urea = 1 


to 24. 



ABNORMAL CONSTITUENTS OF URINE 373 

The discussion of a few examples based upon actual analyses, 
may serve to show deductions which may be drawn from analyses 
of saliva and urine. 

No. 1.* 
URINE. Name. Date, 

Anal, for Dr. C. A. J. 

24 h. Am't. 2000 c.c. 

Sp. Gr. 1013. Reaction Ac. + (50°) 

Color =N. Sulph. 

Ind. =+ E. Phos.- 

Bile. A. Phos.- 

Diac. Ac. Acetone = abs. . 

Alb. = SI. possible trace. 

Soluble Salts (cryst.) Occasional sodium oxalate. 
Sediment. Occasional leucocytes, few neck of bladder cells, an excess of 
mucin. 

ANALYSIS OF SALIVA. 
Dr. C. A. J. February, 1906. 

Appearance = cloudy. Odor = slight. 

Reaction = strongly acid. Specific gravity = 1003. 

Mucin = slight. Albumin = marked. 

Ammonia = increased, but inferior to Glycogen = negative. 

sulphocyanate which is very high. 
Chlorin = normal or slightly increased. 
Soluble salts = lactates, alkaline chlorids. 
Abnormal constituents = lactic acid. 
Sediment = heavy, excess of leucocytes, 

mucin, and squamous epithelium. 
Indicated diathesis = hyperacid. 

As we study these analyses, we notice first in the urine an 
increased quantity with low urea. These things accompany 
chronic kidney disease, but inasmuch as in this case we find no 
casts in the sediment, and no more albumin than can be ac- 
counted for by the slight irritation at the neck of the bladder, 
we consider the dilution unimportant. The uric acid is high 
in proportion to the urea, and the chlorin being nearly normal 
for the twenty-four-hour amount would indicate a full diet 

* The abbreviations used in this analysis are as follows: N = normal, Ac.= 
acid, SI. = slight. The minus sign = diminished or decreased, the plus sign = ex- 
cessive or increased, Abs. = absent. 



374 



URINE 



with perverted oxidation. These indications are of probabil- 
ities rather than positive conclusions, although in this partic- 
ular case the actual facts were as indicated. The high indoxyl 
in the absence of any acute disease would indicate an increased 
putrefaction in the small intestine, probably due to defective 
intestinal digestion. 

The condition of the saliva, together with the urine analysis, 
would indicate a condition favorable to erosion of the teeth 
and the development of pyorrhoea. It was found that the 
patient was not suffering from erosion of the teeth, except in 
a very slight degree, but the evidences of pyorrhoea were quite 
marked at the time of the first examination some weeks before 
the analyses were made. 



No. 2. 



URINE. 



Name. 



Date, 





Per cent. 


Grams in 
24 hours. 




Urea 2.27 


25.24 


Reaction = Ac. 


Uric Ac. 0.051 


0.61 


Sulph. 


Ammon. 




E. Phos. = N. 


Chlor. . 834 


10. 1 


A. Phos. = N. 


Phos. Ac. 0.112 


i-3 


Acetone = Abs. 


Sugar Abs. 






Uric Ac. to Urea = 1 


to 



Anal, for 

24 h. Am't. 1200 c.c. 
Sp. Gr. = 1023 
Color = SI. high. 
Ind. N. 
Bile. 

Diac. = Ac. 

Alb. SI. possible trace. 
Soluble Salts (cryst.) 
Sediment. — Numerous large calcium oxalate crystals, occasional uric- 
acid crystals, excess of mucin, rarely a blood globule. 

The saliva accompanying this sample indicated a hyper- 
acid diathesis and a slight amount of pus in the sediment, 
otherwise nothing abnormal. In this sample we notice a con- 
centrated urine with a tendency to precipitation of crystalline 
elements which have apparently produced a slight irritation of 
the urinary passages, as indicated by the blood globules, and the 
slightest possible trace of albumin. The patient in this case 
was a young man in good general health, a student at the Dental 
School. An incipient pyorrhoea had been noticed, and, as a 
result of information gained by this analysis, the red meat, 
coffee, and other uric-acid-producing foods were wholly elimi- 



ABNORMAL CONSTITUENTS OF URINE 



375 



ated from the diet, and improvement of the conditions of teeth 
and gums followed. It is not necessary to assume that the 
next case of this character would respond to similar treatment. 



URINE. 



Name. F. J. 



No. 3. 

Date, Dec. '05. 



Phys. Dr. R. 



24 h. Am't. = 22oo c.c. Sp. Gr. 


= 1026 


N.% 


Grams in 
24 hours. 


N. 


Color =N. Reaction =Ac.+ Urea 


= 2.65 


(2.0) 


58.3 


(28.0) 


Uph. =SL- Uric Ac. 


= 0.047 


(0.033) 


1.03 


( 0.5) 


Ind. =S1.- E. Phos. =N. Chlor. 


= 0.625 


(0.67) 


13.7 


(10. 0) 


Bile =Abs. A. Phos. =N. Phos. Ac. 


= 0.16 


(0.18) 


3-5 


( 2.7) 



Acetone very slight trace. Sugar = slight trace present. 
Alb. = SI. possible trace. 

Sediment. — Calcium oxalate crystals very numerous, occasional leuco- 
cyte, occasional blood globule with rarely a hyaline cast. 

(The numbers in parentheses are the average normal.) 

This urine was from a patient with a tendency to diabetes who 
was living almost exclusively on a protein diet. This accounted 
for the high uric acid and high urea. There was a slight irritation 
of the kidneys which was secondary to the glycosuria. There was 
no trouble with the teeth and no examination of saliva was made. 

The following sample indicates a chronic disease of the kidneys, 
and it was thought wise to have the day and night twelve-hour 
quantities measured separately as, in cases of chronic kidney 
disease, the night quantity usually exceeds the day quantity, 
and this fact is often a valuable aid in determining the character 
of kidney disturbances. The metabolism in this case is good, 
the nephritis being only at an early stage. 



No. 4. 



URINE. 



Name. 



Date, 



Anal, for 




Per cent. 


Grams in 
24 hours. 


24 h. Am't. 2500 c. 




Urea 1.01 


25-25 


Sp. Gr. 1012. 


Reaction N. 


Uric Ac. 0.020 


0.50 


Color pale. 


Sulph. 


Ammon. 




Ind.- 


E. Phos.- 


Chlor. 0.315 


7.87 


Bile. 


A. Phos. 


Phos. Ac. 0.90 


2.25 


Diac. Ac. 


Acetone Abs. 


Sugar Abs. 




Alb. SI. trace. 




Uric Ac. to Urea = 1 


to 


Soluble Salts (cryst.). 






Sediment. — Squamous epithelium 


with several hyaline and i 


ine granular 


casts. 









376 



URINE 



The following is a case of chorea and is of interest, particu- 
larly, on account of the large number of sodium oxalate crys- 
tals which were persistently present. 



URINE. Name. M.G. 



No. s. 
Date, March 28, 1912. 



Anal, for 



473 c.c. 





Per cent. 


Grams in 
24 hours. 




Urea 2.31 


10.93 


Reaction Ac. 


Uric Ac. 0.053 


0.251 


Sulph. 


Ammon. 




E. Phos. 


Chlor. 0.588 


2.781 


A. Phos. 


Phos. Ac. 0.135 


0.638 


Acetone Abs. 


Sugar Abs. 




;e. 


Uric Ac. to Urea = 


1 to 



24 h. Am't. 

Sp. Gr. 102 

Color, SI. high. 

Ind. N. 

Bile. 

Diac. Ac. 

Alb. SI. possible trace. 

Soluble Salts (cryst.). Sodium oxalate crystals, phosphatic crystals. 

Sediment. — Leucocytes, epithelium. 

As seen by these examples, it is necessary to take the whole 
analysis into consideration, often in conjunction with an analysis 
of the saliva, in order to know just what the system is doing, 
and whether there is possible systemic derangement which 
may have an important bearing on conditions found in the oral 
cavity. Experience and study alone will enable one to correctly 
interpret the results of such analyses, but it has been our aim 
to give sufficient groundwork for the prosecution of such study, 
and to show that in many cases the knowledge derived from 
thorough examinations may be of the greatest importance in 
the successful treatment of diseased conditions. 



APPENDIX. 



Ammonia (dilute). — Strong ammonia one part, distilled 
water two parts. 

Ammonium Molybdate Solution for Phosphates. — This may 
be made by dissolving 20 grams of ammonium molybdate in a 
mixture of 250 c.c. NH 4 OH and 250 c.c. of water. Then this 
solution is added to 1000 c.c. of nitric acid making 1500 c.c. of 
reagent. In using this solution as a test for phosphates it is 
necessary to heat the mixture to about 6o° C. The test is less 
delicate than if made with reagent prepared as follows : 

Dissolve 100 grams of molybdate trioxid (molybdic acid) 
in 400 c.c. of dilute NH 4 OH (10%). Allow to cool and add 
all at once 1000 c.c. of dilute HN0 3 (HN0 3 3 parts, H 2 2 parts). 
The precipitate first formed is immediately redissolved and the 
product should be a perfectly clear, nearly colorless solution. 
This reagent acts in the cold, is more sensitive than that pro- 
duced by the first formula and is recommended as the better of 
the two. 

Barfoed's Reagent. — Dissolve one part of copper acetate 
in fifteen parts of water; to each 200 c.c. of this solution add 
5 c.c. of acetic acid containing 38 per cent of glacial acetic acid. 

Congo Red. — Two per cent aqueous solution. 

CuS0 4 Solution. — One per cent for Biuret test. 

Preparation of Cystin, Tyrosin, and Leucin. 

Cystin. — 1. Clean 200 grams of hair by washing with dilute 
HC1 and then with ether. Boil the clean hair with 600 c.c. of 
concentrated HC1 (specific gravity, 1.19) for four hours (in a 

377 



378 APPENDIX 

three-liter flask with condenser) on a sand-bath in hood. Then 
let cool. 

2. Add concentrated NaOH solution (750 c.c. H 2 0, 500 
grams NaOH) till the reaction is only faintly acid. 

3. Add to the solution, which has begun to boil on neu- 
tralization, plenty of animal charcoal, and boil three-quarters 
of an hour. 

4. Filter hot, being careful to moisten filter and funnel with 
hot water to prevent funnel from cracking. 

5. The filtrate should be faintly yellow. On cooling, a 
crystalline precipitate forms, mainly cystin, with some tyrosin 
and leucin. If this is not the case, or if the precipitate is slight, 
the solution must be concentrated. Save the filtrate, which 
with the filtrate from 6 is to be worked up later for tyrosin 
and leucin. 

6. After standing overnight filter off the precipitate. 

7. Dissolve this precipitate in 350 c.c. of hot 10 per- cent 
NH4OH (hood) and let cool. Then continue the cooling with 
finely chopped ice or with snow. Filter off any tyrosin that 
may have precipitated, and combine it with the filtrate 
of 6. 

8. Add glacial acetic acid, being careful not to acidify. The 
precipitate is a mixture of tyrosin and cystin. Filter. 

9. Make filtrate from 8 quite acid with glacial acetic acid. 
The precipitate is almost pure cystin. Let stand twenty-four 
hours. Then filter, and wash with H 2 and alcohol. 

10. Recrystallize by redissolving in as little hot 10 per 
cent ammonia as is necessary to effect solution, cooling and 
precipitating with glacial acetic acid. 

The preparations should be pure and contain no tyrosin, 
for which test may be made with Millon's reagent. 

Reactions. — Put a trace of cystin into a test-tube with some 
dilute NaOH and a little lead acetate. Boil. H 2 S is formed 
because S is split off. 



APPENDIX 379 

Tyrosin. — i . Concentrate the neutralized nitrate of 6 of 
cystin preparation till, on cooling, tyrosin crystallizes out. 

2. Filter, and save nitrate for the preparation of leucin. 

3. Dissolve the tyrosin crystals in very little hot water. 

4. Add amyl alcohol till a heavy precipitate forms. 

5. Filter precipitate. 

6. Redissolve in very little hot water, and let crystallize 
out by cooling. 

Examine crystals under the microscope. 
Test with Millon's reagent. 

Leucin. — 1. Take the nitrate of 2 in the preparation of 
tyrosin, and evaporate to dryness on the water-bath. 

2. Extract with alcohol. 

3. On standing, the leucin crystallizes out of the alcoholic 
extract as it evaporates. 

4. Filter, and dry the crystals. 
Examine under the microscope. 

Dimethyl-amino-azobenzene.— 0.5 per cent alcoholic solution. 
Esbach's Reagent. — See page 360. 

Fehling's Solution. — The Fehling's solution recommended 
for experiments in this book is one-half the strength frequently 
employed, and is prepared in separate solutions as follows: 
Dissolve 34.639 grams of pure crystallized copper sulphate in 
water, and make solution up to one liter. This constitutes the 
first part of the reagent. The second part may be made by 
dissolving 173 grams of Rochelle salt and 52.7 grams of caustic 
soda (NaOH) in water and making up to one liter. When pre- 
pared in this way 10 ex. of each of these solutions mixed to- 
gether will be reduced by 0.05 gram of glucose. 

Ferric Chlorid. — 2.5 per cent. Solution acidified with HC1. 

Glycogen (C 6 Hio0 5 )n. — Use a liver taken from an animal 
just killed, or, if the season permits, oysters just removed from 
the shell. Cut an oyster, as rapidly as possible, into small 
pieces, and throw it into four times its weight of boiling water, 



380 APPENDIX 

slightly acidulated with acetic acid. After boiling the first por- 
tion for a short time, remove the pieces, grind in a mortar with 
some sand, return to the water, and continue the boiling for sev- 
eral minutes. Filter while hot. The opalescent solution thus 
obtained is an aqueous solution of glycogen and other substances. 

If a purer solution is desired, continue as follows: Add 
to the filtrate alternately a few drops of HC1 and potassio- 
mercuric iodid, until a precipitate of protein ceases to form. 
This may be determined more conveniently by filtering off 
a small portion of the liquid from time to time, and adding to 
the clear filtrate the HO and potassiomercuric iodid. When 
the precipitation of the proteins is complete, filter, and to the 
milky filtrate add double its volume of alcohol; the glycogen 
will precipitate as a white powder. Filter this off, wash with 
66 per cent alcohol (one part of water to two of alcohol), and 
dissolve in water. 

Gram's Solution. — Same as Iodin Solution given below. 

Gunzburg's Reagent. — Phloroglucin, 2 grams; vanillin, 1 
gram; alcohol, 100 c.c. 

Hydrochloric Acid (dilute). — Hydrochloric acid, strong, 
(sp. gr. 1.20) one part; distilled water, two parts. 

Hypobromite Solution for Urea. — Consists of a mixture of 
equal parts of the following solutions: 

Bromin Solution for Urea. — 125 grams KBr and 125 grams 
Br to one liter water. 

NaOH Solution for Urea. — A 40-per cent solution. 

Iodin Solution. — 10 grams iodin, 20 grams KI, made up 
with water to one liter. 

Iodin Tincture. — See tincture. 

Invertase. — Mix 500 gms. of " beer yeast," 200 c.c. of water 
and 10 gms. of sugar, allow to stand one hour. Add 50 c.c. of 
60% alcohol and a little thymol. Filter, press or allow to dry, 
put the nearly dry mass in a flask, add 20 gms. of sugar and 
shake till solution is effected. Keep in ice chest. 



APPENDIX 381 

If "beer yeast" is not available a solution of invertase, rather 
less satisfactory than the above, can be made as follows: Take 
one dozen compressed yeast cakes, grind with sand and mix 
with 500 c.c. of water, and a little chloroform as preservative. 
Allow to stand twelve hours and filter. 

Leucin. — See under Cystin, pages 377, 379. 

Lipase. — From castor bean. Remove the shells from 10 
grams of fresh beans, break them up as fine as possible and 
allow to stand overnight in a loosely stoppered test-tube full of 
alcohol ether mixture. Pour off; grind the beans to a powder 
in a small mortar, transfer to a test-tube and let stand under 
ether overnight. Filter with suction filter and wash two or 
three times with small amounts of the alcohol ether mixture. 

Fat Digestion with Lipase {castor bean). — Grind with the 
powder, in the order named, 5 c.c. N/10 sulphuric acid (sup- 
plied), 5 c.c. of neutral cotton oil (sp. gr. 0.92) and 5 c.c. luke- 
warm water. The water should be added a little at a time and 
thoroughly worked into the mixture so that at the end of the 
operation a good emulsion is secured. Cover the evaporating 
dish and let stand in a warm place overnight. 

Add 50 c.c. of alcohol, 10 c.c. ether, and a few drops phenol- 
phthalein and titrate with N/i sodium hydrate. Calculate 
the amount of fatty acid and the per cent of fat digestion. 

Lipase. — From pancreas. Take a pig's pancreas, remove 
all fat, grind and allow to stand overnight. Then add four 
times its weight of 25% alcohol and allow to stand three days. 
Syphon off clear fluid and neutralize with sodium carbonate. 
The solution will contain a fat-splitting enzyme. 

Magnesia Mixture. — 125 grams of ammonium chlorid, 
125 grams of magnesium sulphate, dissolved in sufficient water 
to make one liter of solution, then add 125 c.c. of strong am- 
monia water. 

Mercuric Chlorid Solution. — Five per cent HgCl 2 in dis- 
tilled water. 



382 APPENDIX 

Millon's Reagent. — To one part of mercury add two parts 
nitric acid of specific gravity 1.4, and heat on the water-bath 
till the mercury is dissolved. Dilute with two volumes of water. 
Let the precipitate settle, and decant the clear fluid. 

Mucin Solution. — Cut a portion of a navel-cord into small 
pieces. Shake in a flask with water, changing the water several 
times. This removes salts and albumin. Extract for twenty- 
four hours with lime- water or baryta- water in a corked flask. 
Filter. To filtrate add acetic acid, which precipitates the mucin. 
Let settle, filter, and wash with water. 

Mucin may also be prepared from the saliva by precipitation 
with acetic acid. 

Nessler's Solution. — This is an alkaline solution of mercuric 
iodid, made as follows: Dissolve 35 grams of potassium iodid in 
about 200 c.c. of water. Dissolve 17 grams of mercuric chlorid in 
300 c.c. of hot water. Add the potassium iodid to the mercuric 
chlorid, until the precipitate at first formed is nearly all redis- 
solved. If the precipitate should entirely dissolve, add a few 
cubic centimeters of a saturated solution of mercuric chlorid, 
until a slight permanent precipitate is obtained. After the 
mixture is cold, make up to one liter with a 20-per-cent solution 
of caustic potash. Allow to settle and use the clear solution. 

Nitric Acid (dilute). — Strong HN0 3 (Sp. gr., 1.42) one part, 
and water three parts. 

Pancreatic Extract. — Obtain a fresh pancreas and soak in 
four times its weight of 25% alcohol for two or three days. 
Filter and make the solution neutral or very slightly alkaline 
with sodium carbonate. This solution will contain the fat- 
splitting enzyme. 

Phenoldisulphonic Acid. — Phenoldisulphonic acid, for esti- 
mation of nitrates in water analysis, may be prepared by heat- 
ing on a water-bath for several hours a mixture of 555 grams of 
concentrated sulphuric acid and 45 grams of pure carbolic-acid 
crystals. 



APPENDIX 383 

Phenyl-hydrazine Solution. — 1 gram phenyl-hydrazine hy- 
drochloric! and 2 grams sodium acetate dissolved in 10 ex. 
water. 

Picric-acid Solution (Esbach's Reagent). — Picric acid, 10 
grams; citric acid, 20 grams; dissolved in sufficient water to 
make one liter. 

Potassium Ferrocyanide Solution. — Ten per cent K 4 Fe(CN) 6 
in distilled water. 

Potassium Cyanid (KCNO). — Melt in an iron ladle, of at 
least 50 c.c. capacity, five grams of commercial potassium cyanid, 
and stir in gradually 20 grams of litharge. When the entire 
amount has been added, pour the mass out upon an iron plate, 
and allow to cool. Separate as far as possible the reduced lead 
from the potassium cyanid that has been formed, powder the 
latter, and dissolve in 25 c.c. of cold H 2 0. Filter if necessary 
and purify by repeated crystallization. 

Silver-nitrate Solution. — Drop solution, 1 : 8. 

Quantitative Solution for Chlorin Titration in Urine. — 29.075 
grams AgN0 3 , made up to one liter with water. 1 c.c. of this 
solution corresponds to 0.0 1 gram NaCl or 0.00607 gram CI. 

Starch Paste (thin). — Rub about one-half gram of starch to 
a thin paste with cold water. Add sufficient boiling water to 
dissolve, then dilute to 100 or 150 c.c. 

Sulphuric Acid (dilute). — Twenty per cent strong H 2 S0 4 in 
distilled water. 

Tincture Iodin for Bile Test. — Dilute until just transparent 
in test-tube. 

Tropaeolin 00. — Saturated alcoholic solution. 

Tyrosin. — See paragraph under Cystin, pages 377, 379. 

Uffelmann's Reagent. — Mix 10 c.c. of a 4-per-cent solution 
of carbolic acid with 20 c.c. of water, and add a drop or two of 
ferric chlorid. 

Urea. Synthesis of. — Add to the filtered solution of KCNO 
(above) a cold saturated solution of ammonium sulphate, con- 



384 



APPENDIX 



taining at least six grams of (NH) 2 S0 4 . Heat the mixture 
slowly on a water-bath at a temperature of 6o° C, and main- 
tain at that point for one hour. By this process ammonium 
cyanate is formed and then changed to urea, which may be 
obtained in an impure state by evaporating the solution to dry- 
ness on a water-bath, and extracting the residue with hot, strong 
alcohol. The urea will crystallize from the alcohol as it cools. 



APPENDIX 



385 



INTERNATIONAL ATOMIC WEIGHTS, igi2. 





Symbol. 


Atomic 
Weight. 


Aluminium 


Al 


27.1 


Antimony. . 


Sb 


120. 2 


Argon 


A 


39-88 


Arsenic .... 


As 


74.96 


Barium. . . . 


Ba 


137-37 


Bismuth. . . 


Bi 


208.O 


Boron 


B 


II .0 


Bromin. . . . 


Br 


79.92 


Cadmium . . 


Cd 


I 1 2 . 40 


Caesium. . . 


Cs 


132.81 


*Calcium. . . 


Ca 


40.07 


Carbon. . . . 


C 


12.00 


Cerium .... 


Ce 


140.25 


Chlorin. . . . 


CI 


35-46 


Chromium . 


Cr 


52.O 


Cobalt 


Co 


58.97 


Columbium 


Cb 


93-5 


Copper. . . . 


Cu 


63 -57 


Dysprosium 


Dy 


162.5 


*Erbium 


Er 


167.7 


Europium. . 


Eu 


152.0 


Fluorin .... 


F 


19.0 


Gadolinium 


Gd 


157-3 


Gallium. . . 


Ga 


69.9 


Germanium 


Ge 


72.5 


Glucinum. . 


Gl 


9.1 


Gold 


Au 


197.2 


Helium. . . . 


He 


3-99 


Hydrogen. . 


H 


1 .008 


Indium .... 


In 


114. 8 


Iodin 


I 


126.92 


Iridium .... 


Ir 


193- 1 


*Iron 


Fe 


55-84 


Krypton. . . 


Kr 


82.92 


Lanthanum 


La 


139.0 


Lead 


Pb 


207.10 


Lithium. . . 


Li 


6.94 


Lutecium. . 


Lu 


174.0 


Magnesium 


Mg 


24.32 


Manganese 


Mn 


54-93 


*Mercury . . . 


Hg 


200.6 



Molybdenum 

Neodymium 

Neon 

Nickel 

*Nitron (radium emanation) 

Nitrogen 

Osmium 

Oxygen 

Palladium 

Phosphorus 

Platinum 

Potassium 

Praseodymium 

Radium 

Rhodium 

Rubidium 

Ruthenium 

Samarium 

Scandium 

Selenium 

Silicon 

Silver 

Sodium 

Strontium 

Sulphur 

*Tantalum 

Tellurium 

Terbium 

Thallium 

Thorium 

Thulium 

Tin 

Titanium 

Tungsten 

Uranium 

*Vanadium 

Xenon 

Ytterbium (Neoytterbium) 

Yttrium 

Zinc 

Zirconium 



Symbol 



Mo 

Nd 

Ne 

Ni 

Nt 

N 

Os 

O 

Pd 

P 

Pt 

K 

Pr 

Ra 

Rh 

Rb 

Ru 

Sa 

Sc 

Se 

Si 

Ag 

Na 

Sr 

S 

Ta 

Te 

Tb 

Tl 

Th 

Tm 

Sn 

Ti 

W 

U 

V 

Xe 

Yb 

Yt 

Zn 

Zr 



Atomic 
Weight. 



10 
.6 
4 
9 



96.0 

144-3 
20. 2 
58.68 

222.4 
14.01 

190.9 
16.00 

106.7 
31 04 

195-2 
39 

140. 

226. 

102 

85.45 
101 .7 

1504 
44.1 

79.2 
28.3 

107.88 
23.00 
87.63 
32.07 

181. 5 

127.5 
159-2 
204.0 
232.4 
168.5 
119. o 

48.1 

184.0 

238.5 

510 

130.2 

172.0 

89.0 
65-37 

90.6 



* Values that have been changed. 



INDEX 



A. 

Absolute temperature, 8 

Acetaldehyd, 198 

Acetamid, 226 

Acetanilid, isocyanid test for, 229 

Acetate, 94 

Acetic acid, 212, 213 

Acetic acid, (N/10) factor, 144 

Acetic acid, test for (acetates), 94 

Acetic ether, 207 

Acetic anhydrid, 214 

Acetone, 202 

bodies, 221 

chloroform, 167 

in blood, 202 

in saliva, determination of, 321 

in saliva, 312 

in urine, 364 
Acetylene, 190 

preparation of (Exp. 53), 193 
Acetyl chloride, 214 

urea, 234 
Achroodextrin, 264 
Acid albumin, 278 

albuminate, 278, 291 

ammonium urate, 369 

defined, 3 

groups, 87 

lactates in urine, 369 

metaprotein, 291 

metaprotein, preparation of (Exp. 
192), 293 

phosphates, in urine, 369 

potassium oxalate, 218 

protein, 276 

salts, 3 

urates (ammonium and sodium), 369 
Acids of group I, tests for, 87 

of group II, tests for, 89 

of group III, tests for, 92 

of group IV, tests for 94 
Acidity of saliva, 304 

of urine, determination of, 346 
Acoin, 164 
Acrylic acid, 216 

acid series, 216 



Acrylic aldehyd, 216 
Activators, 255 
Addition products, 186 
Adenin, 236 

Adjacent hydrocarbons, 241 
Adnephrin, 165 
Adrenalin, 165 

chlorid 165 
Adrenol, 165 
Alabaster, 62 
Albumin, 278 
Albumin in saliva, 308 

in saliva, method of determination, 
Dr. H. C. Ferris, 324 

in urine, detection of, 358 

in urine, Esbach's test, 360 

in urine, heat test, 359 

in urine, nitric acid test, 359 
Albuminoids, 274, 282 
Albuminoscope, 359 
Albumins, defined, 273 
Albumose, 291, 2Q3 
Alcohol, 197 

amyl, 198 

ethyl, 197 

methyl, 197 
Alcoholates, 195 
Alcohols, 195 

atomicity of, 196 

classification of, 196, 197 
Aldehyd, 198 

acetic, 198 

acrylic, 216 

benzoic, 247 

formic, 170, 198 
Algaroth, powder of, 32 
Aliphatic hydrocarbons, 186 
Alkali albumin, 278 

albuminate, 278, 2qi 

metaprotein, 291 
Alkali protein, 276 
Alkalimetry, 142 
Alkaline earths, 59 

metals, 69 
Alkalinity of saliva, 304 
Alkaline phosphates (in urine), 354 



387 



338 



INDEX 



Alkyl (term defined), 195 
Alkylated ureas, 234 
Aloxan, 236 
Alloys, analysis of, 157 

blank form for preparation of, 135 

denned, 108 

dental, composition of, 117 

of bismuth, 25 

of cadmium, 26 

of copper, 21 

of lead, 18 

of mercury, 16 

of silver, 14 
Alloys, preparation of, 109 
Allylene, 190 
Alum, 45 
Aluminates, 45 
Aluminium, 45 

alloy for bridgework, 45 

bronze, 108 

solder, 128 

sulphate, 45 
Alypin, 165 
Alypin nitrate, 165 
Amalgam alloy, 108 
Amalgamation process (silver ore), 14 
Amalgam, defined, 108 
Amalgams, method of making, 112 

tests for, 118 
Ames's oxyphosphate of copper, 123 
Amido acids, 221 
Amids, 226 

Amino-acetic acid, 221, 222 
Amino-acids, 221 
Amino-acids in saliva, 320 
Amino-benzene, 246 
Amino-ethyl-sulphonic acid, 223 
Amino-formic acid, 222 
Amino-glutaric acid, 223 
Amino-isobutyl-acetic acid, 222 
Amino-succinic acid, 223 
Amino- valeric acid, 222 
Amins, 226 
Ammonia, 78 

alum, 45 

determination in urine, 352 

dilute, 377 

process (Na^CC^), 73 
Ammoniacal silver nitrate solution, 351 
Ammoniated mercury, 23 
Ammonia test, Folin's, 320 
Ammonium, 75 

acetate, 77 

amalgam, 114 

bifluorid, 165 



Ammonium carbamate, 222 

carbonate, 76, 222 

chlorid, 76 

chlorid in saliva, 309 

hydroxid, 76 
Ammonium magnesium phosphate 
(microchemical formation), 162 
Ammonium molybdate, 377 
Ammonium nitrate, 77 
Ammonium phosphate, 77 
Ammonium phosphomolybdate, 162 
Ammonium picrate (Exp. 118), 252 
Ammonium platinic chlorid, 7,7 

microchemical formation of , 162 
Ammonium salts in saliva, 309 
Ammonium salts in saliva, determina- 
tion, 319 
Ammonium sodium phosphate, 78 
Ammonium sulphate, 77 
Ammonium sulphid, 77 
Amoss, Dr. H. L., phenolphthalin, Ref., 

311 
Amphoteric reaction of milk, 287 
Amyl acetate, 208 
Amyl alcohol, 198 
Amyl butyrate, 208 
Amyl nitrite, 208 
Amyl valeriate, 215 
Amylolytic enzymes in saliva, 322 
Amylopsin, 337 
Anaestheaine, 166 
Analytical groups, 13 
Analytical reactions of arsenic, 27 
Analysis by precipitation, 148 

in dry way, 96 

of groups (see Groups) 

of groups in outline, 82 to 84 inc. 

of saliva, 3 14 
Anesthol, 166 
Aniline, 246 

oil, 246 

preparation of (Exp. in), 251 
Annealing of alloys, no 
Annealing of gold and platinum, in 
Anti-albumin, 279 
Anti-alb uminate, 279 
Anti-albumose, 279 
Antifebrin, isocyanid test for, 229 
Antimony, alloys, 31 

butter of, 32 

in dental alloys, 116 

metal, 31 

oxy chlorid, 32 

potassium tartrate, 221 



INDEX 



389 



Antimony stains, test for, 33 

Antimonyl salts, 31 

Antiseptic tablets, 23 

Apatite, 62 

Apple essence, 215 

Arabinose, 258 

Argols, 71 

Argyrol, 166 

Arington's alloy, 117 

Aristol, 166 

Arsenical pyrites, 26 

Arsenic, antidote for, 27 

Arsenic compounds, 26 

Arsenic hydrid, 27 

Arsenic, in urine, determination of, 366 

reactions for, 27 

special tests, 28 to 31 inc. 

stains, tests for, 33 

volumetric determination, 148 
Arsenious acid, 26 
Artificial enamel, 123 
Asbestos, 63 
Asparaginic acid, 223 
Asparagus, succinic acid in, 218 
Aspartic acid, 223 
Ash in saliva, 325, 326 
Atomicity of alcohols, 196 
Atoms, defined, 1 
Atropine and test, 166 
Aqua regia, 38 
Aurum, 34 

Available oxygen in H2O2 , 146 
Avogadro's law, 9 

B. 

Babbitt's metal, 126 

potash, 72 
Base, defined, 3 

metal, 12 
Basic acetate of lead, 18 

salts, 3 
Bastard metals, 12 
Banca tin, ^3 
Barfoed's reagent, 377 

test (Exp. 139), 262 
Barium, 60 

hydroxid, 60 

peroxid, 60, 171 

salts, flame test, 61 

sulphate, 60 
Baryta water, 60 
Basicity of acids, 212 
Bayberry wax, 215, 268 
Bell-metal, 108 
Benzaldehyd, 247 



Benzene, 240 
Benzine, 187 
Benzoated lard, 247 
Benzoates, 247 
Benzoic acid, 247 
Benzol, 240 
Benzosulphinid, 175 
Benzoyl-glycocoll, 248 
Beryllium, 59 

test for in cement, 124 
Berzelius' test for arsenic, 29 
Bile, 338 

experiments with, 340 

in urine, 365 

pigments, Gmelin's test, 341 

salts, preparation of (Exp. 239), 341 
Binary amalgams, 113 
Biogen, 171 
Bismuth alloys, 25 

analytical reactions, 25 

compounds, 25 

in dental alloys, 116 

metal, 24 

ochre, 25 
Biuret, 233 

formation of, (Exp. 100), 238 

reaction, 277 
Black &■ Sanger, Gutzeit's test, 31 
Black ash, 73 
Black wash, 17 
Blaud's pills, 44 
Block tin, ^ 
Blood, 294 

corpuscles, 295 

corpuscles, number of, 296 

in urine, 371 

plasma, 294 

specific gravity (Exp. 204), 299 

spectroscopical examination of, 298 
Blue stone and blue vitriol, 22 
Blow pipe tests, 101 to 103 inc. 
Boas' reagent, 335 

test for HC1, 335 
Bond, defined, 2 
Bone, 283 
Bone-earth, 283 
Borates, 93 
Borax, 167 
Borax-bead, method of making, 51 

test, 103 
Brass, 108 

solder for, 129 
Britannia-metal, 108 
Bromoform, 192 
Bromids, 89 



39° 



INDEX 



Bromid, separation from iodids, 91 

Bronze. 108 

Buckley, Dr. J. P., Europhen, Ref., 169 

Buckley's phenol compound, 174 

Butane, 185, 189 

Butter fat, 208 

Butter of antimony, 32 

Butylene, 189 

Butylene-diamin, 226 

Butyric acid, 213, 214 

Butyrin, 208 

Bynin, 282 



Cadaverin, 226 
Cadmium, alloys of, 26 

amalgam, 115 

analytical reactions, 26 

in dental alloys, 116 

metal, 25 

oxalate (microchemical), 162 
CafTein, 235 
Calamine, 53 
Calcium, 61 

in teeth and tartar, 180 

lactate, 220 

oxalate(micrcchemical), 162 

oxalate in urine, 370 

sarcolactate, 220 

volumetric determination of, 152 
Calc-spar, 61 
Calomel, 16, 17 
Cane sugar. 261 
Carat, denned, 34 

rules for changing, 35 
Carbamic acid, 222 
Carbamid (Urea), 232 
Carbinol, 197 

Carbocyclic compounds, 249 
Carbohydrates, 182 

classification, 258 
Carbolic acid, 167. 1/4, 242 
Carbonates, 87 

titration of, 144 
Carbon dioxide in saliva, 304 
Carbonic acid, 217 

in teeth and tartar, 180 
Carbon, test for, 182 

tetrachlorids, 192 
Carboxyl, 212 
Carnallite, 69 
Carnin, 297 
"C. A. S." alloy, 117 
Casein, 288 
Caseinogen, 288 



Cassiterite, 33 
Cast iron, 43 
Casts, renal, 371 
Catalase, defined, 255 
Cellulose, 265 
Cement, dental, 120 

composition of, 178 

general tests for, 121 
Centigrade scale, 8 
Centinormal solution, 139 
Cerussite, 17 
Chalk, 61 
Chases' copper amalgam alloy, 117 

incisor alloy, 117 
Chemical affinity, 2 
Chemism, 2 
Chili saltpeter, 74 
Chloral, 199 

test for, 211 

alcoholate, 167 

hydrate, 167, 199 
Chlorates, 94 
Chlorethyl, 192 
Chloretone, 167 

microchemical test, 163 
Chlorids, 88, 90 

determination of in saliva, 321 

in urine, 353 
Chlorin, in saliva, titration, 151 

in teeth and tartar, 180 

titration, 152 

in urine titration, 354 
Chloro-chromic anhydrid test, 90 
Chloroform, 168, 191 

preparation of (Exp. 56), 193 

test for, 211 
Cholesterin, 371 

in saliva, 312 
Chromates, 93 
Chrome alum, 46 

iron ore, 46 
Chrome yellow, 18 
Chromic acid, 90 
Chromic anhydrid, 46 

oxid, 46 

salts, 47 
Chromite, 46 
Chromium, 46 
Chromous salts, note, 46 
Chylous urine, 345 
Cinnabar, 16 
Citric acid, 219 
Classification of metals, 12 
Closed chain hydrocarbons, 240 

tube test, 99 



INDEX 



39 1 



Cloudy urine, causes of, 345 
Coagulated proteins, 276 
Cobalt, analytical reactions, 51 
Cobaltite, 51 
Cobalt metal, 51 

separation from nickel, 56 
Cocain, 168, 207 
Cocain and KMnC>4, 162 
Cocain and substitutes, differentiation 
of, 177 

test for, 168 
Coefficients of expansion, 106 
Coefficient of Haeser, 348 
CO, Haemoglobin. 295 
Coin silver, 14, 108 
Collagen, 282, 283 
Colloids, 5 

Coloring matter in urine, 356 
Color reactions for proteins, 277 
Colors of salts, 97 
Color test for amalgam, 118 
Colostrum, 289 
Common solder, 127 
Completed reactions, 4 
Compound ethers, 204, 207 
Compounds, denned, 1 
Conductivity of metals, 105 
Condys' fluid, 53 
Congo red, test for HC1, 335 
Conjugated proteins, 285 
Contraction test for amalgams, 118 
Cook, Dr. G. W., on mucin in saliva, 

Ref., 308 
Cook, Dr. R. H., on determination of 

uric acid, 351 
Cooking soda, 70 
Copper, 21 

acetate, 22 

aceto arsenite, 22 

alloys, 21 

amalgam, 114 

analytical reactions, 22 

arsenate, 22 

compounds, 21 

gravimetric determination of, 156 

in dental alloy, 116 

oxyphosphate (Ames'), 123 

pyrites, 21 

sulphate, 22 

volumetric determination of, 151 
Copperas, 44 

Corrosive sublimate, 23, 172 
Corrugated gold, in 
Cotton seed oil, 217 
Cream of tartar, 17, 221 



Creatin (Exp. 212), 301 

Creatinin (Exp. 213), 301 

Creolin, 246 

Creosote, 168 

Cresol, 168, 246 

Crushing strength of amalgams, 119 

Cryolite, 72 

process (Na2CC>3 ), 73 
Cryoscopy, 9 
Crystalloids, 5 
Crystals, formation of, 160 

from saliva, 326 
Cuprammonium compounds, 22 
Cupric oxid, 22 
Cuprous oxid, 21 
Cyanic acid, 233 
Cyanic acid (iso.), 229 
Cyanids, 88 
Cyanogen, 228 
Cyanuric acid, 233, 236 
Cyclic compounds, 249 
Cylinder oil, 187 
Cystin, 223 

in urine, 370 

preparation of, 377 
Cysto-globulin, 275 



Decinormal factor, 139 

solutions defined, 139 

solutions (various), 142 to 153 
Defibrinated blood, 295 
Degree of acidity explained, 287 
Dental alloys, 108 

composition of, 117 

cement, 120 

gold, 108 
Dentine, composition of, 178 
Derived albumins, 278 
Derived proteins, 275, 2Qi 
Deutero-albumose, 293 
Dextrin, 264 
Dextrose, 259 
Diabetic sugar, 259 
Diacetic acid in urine, 365 
Diacylon plaster, 18 
Dialysis, 6 

of saliva, 327 
Diamins, 226 
Diastase, 261 
Dibasic acids, 217 
Dichlor methane, 191 
Dilute ammonia, 377 

hydrochloric acid, 380 

lunar caustic, 15 



39 2 



INDEX 



Dilute nitric acid, 382 

sulphuric acid, 383 
Dimethylamin, 226 
Dimethyl-amin-azo-benzene test for 

HC1, 334 
Dimethyl benzene, 241 

ketone, 202 

oxalate, 224 
Dioses, 260 
Dioxypurin, 236 
Disaccharids, 260 
Diureids, denned, 234 
Dolomite, 63 
Donovans' solution, 27 
Doremus-Hinds urea apparatus, 350 
Double bonded hydrocarbons, 189 
Dualistic formulae, 2 
Ductility of metals, 105 
Dyad-mercury, analytical reaction, 24 

compounds of, 23 
Dynamometer, Black's, 113 
Dysalbumose, 293 

E. 

Earthy phosphates in urine, 355 
Edestin, 281 
Egg albumin, 278 
Ektogan, 169 
Elastin, 282, 283 
Electro-properties, 106 
Elements denned, 1 
Eleopten, 267 
Empirical formulae, 2 
Emulsiflcation (Exp. 153), 269 
Enamel, artificial, 123 

composition of, 178 
Endelman on phenolphthalein, Ref, 174 
End point defined, 138 
Enterokinase, 337 
Enzymes, 253 

properties and classification, 254 
Epithelium in urine, 370 
Epsom salt, 63 

Equations, method of balancing, 4 
Erepase, 338 
Erepsin, 338 
Erythrodextrin, 264 
Esbach's reagent, 260 
Essence of checkerberry, 247 
Esters, 204, 207 
Ethane, 188 

Ether, preparation of, 205 
Ethers, 204 
Ethyl acetate, 207 



Ethyl alcohol, 197 
Ethyl benzene, 241 
Ethyl bromid, 192 
Ethyl butyrate, 207 
Ethyl chlorid, 169, IQ2 
Ethylene, 189, 206 

chlorid, 189 

diamine, 226 
Ethyl ether, 205 
Ethyl hydrazine, 227 
Ethylidene lactic acid, 220 
Ethyl mercaptan, 245 
Ethyl nitrite, 208 
Ethyl oxid, 205 
Ethyl urea, 234 
Eucain, 169 
Eucain lactate, 169 
Eudrenin, 169 
Eugenol, 169 
Europhen, 169 
Euzone, 171 

Evaporation, microchemical, 161 
Expansion of metals, 106 
Expansion test for amalgam, 118 
Extraction of metals from ore, n 



Fahrenheit thermometer, 8 

Fat in milk, 289 

Fat in urine, 372 

Fats, 208, 267 

Fatty acids, 212 

Fatty casts, 372 

Fehling's test (Exp. 136), 262 

solution, 379 
Fellowship alloy, 117 
Fen wick, Dr. S., on KCNS in saliva 

Ref., 310 
Fermentation test (sugar), (Exp. 140), 

262 
Ferments, 253 
Ferric alum, 46 

chlorid, 43 
Ferricyanids, 91 
Ferric ferrocyanid, 45 
Ferric sulphate, 43 
Ferric sulphocyanate, 45 
Ferric thiocyanate, 45 
Ferris, Dr. H. C, methods of saliva 

analysis, Ref., 314 
Ferris's ureometer, 320 
Ferrous carbonate, 44 
Ferrous sulphate, 44 
Fibrin, 295 
Fibrin ferment, 294 



INDEX 



393 



Fibrinogen, 294, 300 
Fibrinous casts, 371 
Filtration, 6 

microchemical, 161 
Fine solder, 127 
Fire damp, 188 
Flagg's submarine alloy, 117 
Flame test, 100 
Fleitman's test, 29 
Fletcher's gold alloy, 117 
Flow of amalgam, 102 
Folin's ammonia test, 320 

method for ammonia in urine, 352 
Formaldehyd, 198 

method for ammonia in urine, 352 
Formaldehydurea, 368 
Formalin, 170 

test for (Exp. 62), 201 
Formamid, 226 
Formanilid, 227 
Formic acid, 212, 21 3 
Formic ether, 205 
Formine, 170 
Formol, 170 
Formose, 198 
Formula, defined, 2 
Fowler's solution, 27 
Fractional distillation, 187 
French chalk, 63 
Freund & Topfer, test for acidity of 

urine, 347 
Frohde's reagent, 173 
Fruit sugar, 260 
Fulminic acid, 229 
Furfuraldehyd, 259 
Fusel oil, 198 
Fusible metals, 126 



Gad's experiment (Exp. 153), 269 

Galactose, 260 

Galena, 17 

Gallotannic acid, 176 

Gasolene, 187 

Gastric contents, titration for acidity, 

(Exp. 229), 336 
Gastric digestion, 331 

lipase, 332 
Gay-Lussac, law of, 8 
Gelatine, 283 

preparation of (Exp. 175), 284 
General protein reactions, 276, 277 
German silver, 108 
Glauber's salt, 74 
Gliadin, 282 



Globin 274 

Globulins, 273, 279, 281 
Glonoin, spirit of, 1 73 
Glycerine, see Glycerol 
Glycerol, 170, 209 
Glyceryl, 208 

butyrate, 208 

oleate, 209 

palmitate, 209 

stearate, 209 
Glycin, 222 
Glycocoll, 222 

relation to urea, 338 
Glycocollic acid in bile, 338 
Glycogen, 264 

in muscle, 297 

in saliva, 321 

isolation of, 379 
Glycol, 217 

Glycollic acid, 217, 21 g 
Glyco-proteins, 285 

denned, 275 
Glucinum, 59 
Gluconic acid, 259 
Glucosazone, 260 
Glucose, 259 
Glue, 283 

Glutamic acid, 223 
Glutelins, 282 

denned, 274 
Glutenin, 282 

Gmelin's test for bile (Exp. 240), 341 
Gold, 34 
Gold, aluminium solder, 129 

amalgam, 115 

annealing of, in 

gravimetric determination of, 157 

in dental alloys, 116 

salts, 36 

scrap, recovery of, 133 

solders, 129, 130, 131 

volumetric determination of, 148, 
i54 
Goulard's extract, 18 
Grain alcohol, 197 
Gram's solution, 170, 380 
Grape sugar, 259 
Graphic formulae, 2 
Gravimetric determination, 153 to 158 

inc. 
Gravity, specific, 9 
Green vitriol, 44 
Group I, analysis of, 19 
Group II, analysis of, 37 
Group III, analysis of, 47 



394 



INDEX 



Group IV, analysis of, 55 

Group V, analysis of, 64 

Group reagents, 12 

Groups I-VI, metals of, 13 

Groups III, IV and V. analysis, phos- 
phates present, 80 

Guaiacol, 243 

Guaiacum test for blood (Exp. 205), 
299 

Guanin, 236 

Gun cotton, 265 

Gun metal, 109 

Gunzburg's reagent and test, 334 

Gunzburg's reagent, 380 

Guttapercha, 170 

Gutzeit's test, 28 

Gutzeit's test (Sanger & Black), 31 

Gypsum, 62 

H. 

Haemin, 296 

crystals, preparation of (Exp. 206), 

299 
Haematin, 295 
Haemochromogen, 295 
Haemoglobin, 295 

crystals, preparation of (Exp. 202), 

298 
Haemoglobins denned, 275 
Halogens, test for, 184 
Haloid derivatives of the paraffins, 191 
Hard solder, 127 
Harris's amalgam alloy, 117 
Head, Dr. Joseph, bifluorid of ammonia, 

Ref., 165 
Heavy spar, 60 
Helium, 60 

Hematoporphyrin, 345 
Hemialbumose, 279, 2pj 
Hemipeptone, 279 
Hemostatin, 165 
Heroin, 170 
Hetero-albumose, 293 
Heterocyclic compounds, 249 
Heteroxanthin, 236 
Hexoses, 259 
High grade alloy, 117 
Hippuric acid, 222, 248 
Histones, defined, 274 
Homocyclic compounds, 240 
Homologues, 185 
Hopogan, 171 
Hordein, 282 
Horismascope, 359 
Horn silver, 14 



Howe, Dr. J. Morgan, on KCNS in 

saliva, Ref., 310 
Howe, Dr. Percy R., calcium determi- 
nation, Ref., 152 
Howe, Dr. Percy R., phosphates in 

saliva, 77 
Hydrargyrum, 16 
Hydrazines, 227 
Hydrocarbons, 184 
Hydrochinon, 243 
Hydrochloric acid in stomach, 333 

test for free, 334 
Hydrocyanic acid, 228 
Hydrogen dioxid, see Hydrogen peroxid 

peroxid, 171 

peroxide factor for, 146 

peroxid strength of, 146 

test for, 182 
Hydrolysis, 254 
Hydrolytic enzymes, 254 
Hydroquinol, 243 
Hydroxy acids, 219 
Hydroxy acetic acid, 219 
Hydroxy benzene, see Phenol, 174 
Hydroxy propionic acid, 219 
Hydroxy succinic acid, 219 
Hydroxy toluene, 246 
Hypobromite solution for urea, 380 
Hypochlorites, 90 
Hypophosphites (HH2PO2), 91 
Hypoxanthin, 236 

I. 

Ignition tests, 98 
Indican, see Indoxyl 
Indicators, 140 
Indol, 250 
Indoxyl, 250 

in urine, 357 

oxidation of, 250 

-potassium sulphate, 250 
Inorganic matter in teeth and tartar, 

179 
Inosite, 297 
Invertase, 380 

Iodids and bromids, separation of, 91 
Iodin, decinormal solution of, 147 

test for bile pigment (Exp. 240), 341 
Iodoform, 192 

preparation of (Exp. 57), 94 
Ions, 3 
Iron, 43 

by hydrogen, 43 

compounds of, 43 

reactions of, 44 



INDEX 



395 



Iron, reduction from ore 4 43 

scale, salts of, 221 
Isobenzonitril, 229 

test for chloral, 211 
Isobutylcarbinol, 198 
Isocyanic acid, 229 
Isocyclic compounds, 249 
Isomers, 185 
Isonitrils, 229 



Kalium, 69 

Kekule's benzene ring, 240 

Kephir grains, 289 

Keratin, 282 

Kerosene, 187 

Ketones, 202 

Ketose, 258 

Kieserite, 63 

King's occidental alloy, 117 

Kingzett's method for H2O2 titration, 

147 
Kirk, Dr. E. C, C0 2 in blood, Ref., 312 
Kjeldahl process of oxidation, 183 
Kumiss, 289 



Lacmoid, 140, 243 
Lactalbumin, 288 
Lactates in urine, 370 
Lactic acid, 220 

in muscle, 297 

in tartar, 179 

tests for, 335 
Lactose, 261 
Lactosazone, 261 
Laevulose, 260 
Law of Avogadro, 9 
Law of Charles, 8 
Law of Gay-Lussac, 8 
Law of precipitation, 10 
Lead, 17 
Lead acetate, 18 
Lead alloys, 18 
Lead arsenate, 18 
Lead chromate, 18 
Lead nitrate, 18 

oxids, 18 

reactions of, 19 

reduction from PbS, 17 

subacetate, 18 
Lead in urine, determination of, 366 
LeBlanc process (Na 2 C0 3 ), 72 
Lecithin in saliva, 312 
Lecitho-proteins defined, 275 



Legal 's test for acetone, 364 
Leptothrix, 330 
Leucin, 222, 223 

in saliva, 312 

preparation of (Exp. 231), 339; also; 

377 
Leucocytes, 296 
Limestone, 61 
Lipase, from castor bean, 381 

from pancreas, 381 
Litharge, 18 
Lithium, 75 

salts and uric acid, 237 
Litmus, 140 
Liver of sulphur, 71 
Local anaesthetics, 164 
Low's gold solder, 131 
Lugol's caustic iodin, 171 

solution, 171 
Lunar caustic, 15 
Lymphocytes, 296 

M 

Magnesite, 63 
Magnesium, 63 

carbonate, 63 

in teeth and tartar, 180 

oxid, 64 

peroxid, 171 

phosphates, 64 

sulphate, 63 
Mahe, Dr. G., on NaCl, Ref., 17s 
Malachite blue and green, 21 
Malic acid, 218, 219 
Malleability of metals, 105 
Malonic acid, 218 
Maltodextrin, 264 
Maltose, 261 
Manganates, 53 
Manganese, 52 

hydroxid, 53 

reactions, 53 

separation from zinc, 56 
Mannite, 196 
Marble, 61 

Marme's reagent, 173 
Marsh-Berzelius test for arsenic, 29 
Marsh gas, 188 

Marsh's test for arsenic or antimony, 32 
Mayer, A., on KCNS in saliva, Ref., 310 
McElhinney, Mark G., platinum solder, 

Ref., 131 
Measures, 7 
Meconic acid, 216 
Meerschaum, 63 



30 



INDEX 



M client's metal, 126 
Melting point of metals, 105 

method of taking, 127 
Menthol, 172 
Mercaptan, 245 
Mercuric chlorid, 23, 172 

oxid, 23 

iodid, 23 
Mercurous chlorid, 16 

iodid, 17 

nitrate, 17 
Mercury, 16 

alloys, 16 

compounds of, 16 

excess of, in amalgams, 117 

in saliva, test for, 330 

reactions of, 17 

recovery of, 134 

tests for purity, 134 
Mesitylene, 242 
Meta-compounds denned, 241 
Metacresol, 246 
Metalloids, 12 
Metals, classification, 12 

extraction of, 11 

occurrence of, 11 

properties of, 105 
Metaphosphate of zinc, 120 
Meta-protein, 291 

denned, 275 

preparation of, 292 
Metastannic acid, 33 
Methane, 188 
Methethyl, 172 
Methyl-alcohol, 195, 197 

test for, (Exp. 61), 200 
Methylamin, 226 
Methyl-benzene, 241 
Methyl-bromid, 192 
Methyl-carbamine, 229 
Methyl-carbinol, 197 
Methyl-chlorid, 172, 191 
Methyl-chloroform, 192 
Methylene chlorid, 191 
Methylene ether, 205 
Methyl ether, 205 

ethyl ether, 205 

hydrazine, 227 

iodid, 192 

orange, 140 

oxid, 205 

salicylate, 207 

urea, 234 
Metric equivalents, 7 



Michaels, Dr. J. P., albumin in saliva, 

Ref., 308 
Michaels, Dr. J. P., methods of saliva 

analysis, Ref., 315 
Michrochemical analysis, 159 
Microcosmic salt, 78 
Microscope, use of, 159 
Milk, 286 

alcoholic fermentation of, 289 

fat, 289 

modified, 288 

plasma, 286 

reaction of, 287 

specific gravity of, 286 

solids by calculation, 287 

wine, 289 
Miller, Dr. W. D., mucin in saliva, Ref. 

308 
Millon's reagent, 382 

test (protein), 277 
Mineral oil, 186 
Minium, 18 
Mixed ether, 204 
Modified milk, 288 

Mohr's method of determination of ar- 
senic, 148 
Moisture in teeth and tartar, 179 
Molecules, defined, 1 
Molisch's test (carbohydrates, Exp. 133), 

262 
Monobrommethane, 192 
Monochlormethane, 169 
Monasaccharids, 258 
Monsel's salt, 43 
Monoses, 259 
Morphine, 172 

Morphine, michrochemical test, 162, 163 
Mucic acid, 308 
Mucin, 285 
Mucin in saliva, 307 

in saliva method of determination, 
Dr. H. C. Ferris, 324 

in urine, 372 
Mucoids, 275 
Murexid, note, 236 

test (uric acid, Exp. 104), 239 
Muscle, 296 
Muscle plasma, 296 
Muscle serum, 297 
Musculin, 300 
Myogen, 301 
Myogenfibrin, 301 
Myosin, 297, 300 
Myosinogen, 297 






INDEX 



397 



N. 
Naphtha, 187 
Natrium, 72 
Nessler's reagent, 24 
Neutral salts, 3 
Nickel, 52 

alloys, 52 

coin, 52 

separation from cobalt, 56 
Nirvanin, 173 
Nitrates, 94 
Nitre, 70 
Nitrils, 229 
Nitrites, 91 

in saliva, 310, 322 
Nitrobenzene, 245 

preparation of (Exp. no), 251 
Nitrogen, tests for, 182 
Nitroglycerin, 173 
Noble metals, 12 
Non-cohesive gold, in 
Normal factor, denned, 137 
Normal salt solution (physiological), 

73 
Normal solution, denned, 137 
Novocain, 173 
Nucleo-albumin in bile, 340 
Nucleohistone, 275 
Nucleo-proteins, denned, 275 

O 

Occurrence of metals, 11 
Odontographic alloy, 117 
Oil of betula, 207 

of bitter almonds, 247 

of cloves, 173 

of mirbane, 245 

of wintergreen, 207, 247 
Oils, 267 

Olefin series of hydrocarbons, 189 
Oleic acid, 217 
Organic acids, 212 
Organic chemistry, 181 
Organic matter in teeth and tartar, 180 
Organized ferments, 253 
Orpiment, 26 

Ortho-compounds, denned, 241 
Orthocresol, 246 
Orthoform, 174 
Osazones, 260 
Osmotic pressure, 6 
Osmosis, 6 
Outline analysis, group I- VI, 82 to 84 

inc. 
Oxalates, 89, 93 



Oxalates in urine, 370 
Oxalic acid, 217, 218 

in foods, 218 

standard solution of, 139 

in tartar, 179 
Oxaluric acid, 234 
Oxidation of alcohols, 198 
Oxidases, see Oxydases 
Oxidation and reduction, analysis by, 

144 
Oxyacids, 219 
Oxybenzene, 242 
Oxybenzoic acid, 207 
Oxybutyric acid, 220 
Oxychlorid cements, 122 

of zinc, 122 
Oxydases, 255 

in saliva, 311 

preparation of (Exp. 125), 255 
Oxyhemoglobin, 295 
Oxyphosphate cement, 123 

of copper, 123 

of zinc, 120' 
Oxypropionic acid, 220 
Oxysulphate of zinc, 123 



Palmatin, 215 

Palmitic acid, 213, 215 

Pancreatic juice, 339 

Parabanic, 234, 236 

Para compounds, denned, 241 

Para-cresol, 246 

Paraffin, 187 

series, 185 

wax, 186 
Paraform, 198 
Paraformaldehyd, 198 
Paraglobulin, 281 
Paralactic acid, 220 
Paraldehyd, 199 
Para-myosinogen, 300 
Paris green, 22 
Pearl ash, 70 
Pearson's solution, 27 
Pentane, 185 
Pentoses, 258 
Pepsin, 331 

Pepsin-hydrochloric acid, 333 
Pepsinogen, 331 
Peptides, 276, 292 
Peptones, 276, 292 

Permanganate, standardization of, 145 
Peroxidases, 255 

in saliva, 311 



398 



INDEX 



Peroxid of calcium, 171 

of hydrogen, 171 

of hydrogen, strength 146 

of lead, see Black oxid, 18 

of magnesium, 171 

of sodium, 72, 171 

of zinc, 169, 171 

titration by Na2S203, 147 
Petrolatum, 187 
Pewter, 33 
Phenol, 1/4, 242 

compound, 174 

difference from cresol, 168 
Phenolphthalein, 140, 248 
Phenolphthalin, 311 
Phenol, preparation of (Exp. 124), 252 
Phenol-sulphonic acid, 244 
Phenyl-formamid, 227 
Phenyl-glucosazone, 260 
Phenylhydrazine, 227 

test (Exp. 141), 263 
Phenyl-isocyanid, 229 
Phenyl-salicylate, 247 
Phenyl-sulphuric acid, 245 
Phloroglucinol, 243 
Phosphates, 89, 92, 93 

as urinary sediment, 354 

determination in saliva, 321 

method for determination in saliva 
and urine, 153 
Phospho-proteins, defined, 275 
Phosphoric acid, factor, 355 

in teeth and tartar, 180 

volumetric determination, 153 
Phosphorus, test for, 183 
Phthalic acid, 248 

anhydrid, 248 
Physiological chemistry, 253 
Physiological salt solution, 73 
Picric acid, 246 
Pine-apple essence, 207 
Piotrowski's test (protein), 277 
Plaster compound, 63 
Plaster of Paris, 62 
Plate I, 100 
Plates II and III, 162 
Plate IV, 163 

V, 222 

VI, 261 

vn, 296 

VIII, 327 

IX, 367 

X, 368- 
Platinum, 36 

alloys, 37 



Platinum-aluminum solder, 129 

amalgam, 115 

annealing of, in 

color, for enamel, 37 

in dental alloy, 117 

solder for, 131 
Polymers, 186 
Polyoses, 263 
Polysaccharids, 263 
Potash alum, 45 
Potassio-auric iodid, 36 

-mercuric iodid, 24 
Potassium, 69 

bicarbonate, 71 

bitartrate, 71, 221 

bromate, 70 

bromid, 70 

carbonate, 70 

chlorate, 70 

cyanid, 70, 228 

ethylate, 195 

hydroxid, 6q, 174 

iodid, 70 

iodo-hydrargyrate, 24 

methylate, 195 

nitrate, 70 

permanganate, 52 

phenolate, 242 

platinic chlorid, 37, 71 

sulphid, 71 

sulphocyanate, 229 
in saliva, 309 
standard solution of, 150 
Potato spirit, 198 
Precipitation, 9 

law of, 10 
Primary alcohol, 196, 197 
Prinz, Dr. H., on Phenol-sulphonic acid, 

ref., 244 
Pro-enzymes, defined, 254 
Prolamins, 282 

defined, 274 
Propane, 189 
Propenyl, 208 
Propionic acid, 212, 214 
Propylene, 189 
Protamins, defined, 274 
Proteans, defined, 275 
Protein, defined, 273 
Proteins, 270 

classification of, 270, 273 
Proteoses, 276, 291 
Proto-albumose, 293 
Prosecretin, 339 
Proximate analysis, 182 



INDEX 



399 



Proximate principles, 182 
Prussian blue, 45 
Prussic acid, 228 
Ptomains, 226 

Ptyalin, action on starch (Exp. 214), p. 
3 2 7 

conditions affecting action of, 328 

in saliva, 309 
Pseudo-nucleo albumin, 288 
Purple of Cassius, 36 
Purin, 235 
Putrescin, 226 
Pus, denned, 296 

in urine, 371 
Pyridin, 249 

Pyrocatechin (pyrocatechol) 
Pyrocatechol, 243 
Pyrogallic acid, 243 
Pyrogallol, 243 
Pyrolusite, 52 
Pyro-tartaric acid, 219 



Qualitative analysis, 11 

Quantitative analysis of dental alloys, 

i57 
Quinalin, 249 



Radium, 60 

Reaction of saliva, 303 

Reactions, completed and reversible, 4 

Realgar, 26 

Red blood corpuscles, 296 

Red lead, 18 

test for manganese, 53 
Red precipitate, 24 
Rees's alloy, 33 
Reinsch's test for arsenic, 28 
Renal casts, 371 
Rennin, 332 
Residue, recovery of gold, 133 

of mercury, 134 

of silver, 133 
Resorcinol, 243 
Reversible reactions, 4 
Rhigoline, 174, 187 
Richards, Dr., aluminium alloy, 45 
Richmond, Dr. C. M., fusible alloy, 126 

gold solder, 131 
Rochelle salts, 74, 221 
Rock oil, 187 
Rose's metal, 126 
Rule for changing C. to F. degrees, 8 



S. 
Saccharic acid, 259 
Saccharin, 175 
Saccharose, 261 
Salammoniac, 76 
Saleratus, 70 
Salicylates, 247 
Salicylic, 207, 247 
Saliva, acidity of, 304 

action on starch (Exp. 214), 327 

acetone in, 321 

alkalinity, 331 

ammonium salts in, 309 

analysis of, 314 

carbon dioxid in, 304 

color of, 306 

determination of ammonia, 319 
of ash, 325, 326 
of chlorides, 321 
of nitrites, 322 
of phosphates, 321 
of potassium sulphocyanate, 318 
of solids, 325, 326 
of specific gravity, 317 
of urea, 320 

enzymes in, 322, 323 

glycogen in, 321 

nitrites in, 310 

odor of, 306 

physical properties of, 303 

ptyalin in, 309 

quantity of, 303 

reaction, 303, 317 

specific gravity, 303 

variation in composition, 302 

viscosity of, 315 
Salivary sediment, 330 
Salmine, 274 
Salol, 247 
Sal soda, 72 
Salt defined, 3 
Salt of sorrel, 218 
Saltpeter, 70 
Salts of tartar, 70 
Salt solution, decinormal, 149 
Sanger and Black (Gutzeit's test, Ref.), 

31 
Saponification (Exp. 150), 268 
Sarcolactic acid, 220 
Scale salts of iron, 221 
Secondary alcohol, 196, 197 
Secondary protein derivatives, 276 
Secretin, 339 
Sedimentation, 6 
Sediment in saliva, 330 



4oo 



INDEX 



Seminormal solution, 139 
Semipermeable membrane, 6 
Serum albumin, 278, 294 
Serum, blood, 294 

globulin, 294 
Silicon skeleton, 92 
Silver, 14 

alloys, 14 

amalgam, 115 

decinormal solution of, 149 

fire assay, 157 

gravimetric determination of, 155 

hydroxid, 15 

in dental alloy, determination of, 150 

nitrate, 175 

oxid, 15 

recovery of, 133 

solder for, 131 
Silver-tin alloys, 116 
Silver, titration of, 149 

of by KCyS, 150 
Silvering mirror (alloy used), 33 
Simple ethers, 204 
Simple proteins, 273, 278 
Skatol, 250 

Skatoxyl potassium sulphate, 250 
Smaltite, 51 
Smelling salts, 76 
Smithsonite, 53 
Smoky urine, 345 
Soap, 209 
Soapstone, 63 
Soft solder, 127, 12 8 
Sodium, 72 

amalgams, 113 

bicarbonate, 73 

carbonate, 72 

chlorid, 73, 175 

decinormal solution, 149 

hydroxid, 72 

nitrate, 74 

oxalate in urine, 370 

microchemical crystals, 162 

perborate, 175 

peroxid, 72, 171, 175 

phosphates, 74 
and uric acid, 237 

potassium tartrate, 74, 221 

pyroantimonate, 75 

tetraborate, 167 

thiosulphate n/10 solution, 147 

uranyl acetate, 75 

urate, in urine, 369 

microchemical crystals, 162 
Solder, 127 



Solder for aluminum, 128 

for brass, 129 

for gold, 129 

for platinum, 131 

for silver, 131 
Soldering acid, 128 
Solids in saliva, 325, 326 
Solubility tables, 85, 86 
Soluble cotton, 265 
Solution explained, 5 
Solvay process, 73 
Somnoform, 176 
Specific gravity, 9 

of amalgams, 119 

of saliva, 303 
Spence, Dr. S. J., expansion of plaster, 

ref., 62 
Spermatozoa, 372 
Spirit of Minder erus, 77 
Sputum, 306 
Standard alloy, 117 
Standard dentalloy, 117 
Standard solutions, 137 
Stannous chlorid, 34 
Stannum, ^ 
Starch, 263 

hydrolysis of, 264, 328 

preparation of (Exp. 145), 265 
Steapsin, 337 
Stearic acid, 213, 215 
Stearopten, 267 
Steel, 43 

Sterling silver, 14, 109 
Stibium, 31 
Stibnite, 31 

Stokes, reagent, note, 298 
Stomach steapsin, 332 
Stovain, 176 

Straight chain hydrocarbons, 186 
Stroma of blood corpuscles, 295 
Strontium, 61 

oxalate, michrochemical crystals, 162 

salts and flame test, 61 
Sturine, 274 

Substitution products of the hydro- 
carbons, 184 
Succinic acid, 217, 218 
Sucrose, 261 
Sugar, in saliva, 312 

in urine, 361 

of lead, 18 

quantitative determination by Feh- 
ling's solution, 362 

quantitative determination by fer- 
mentation, 363 



INDEX 



401 



Sugars, 258 

test for, 262, 263 
Sulphanilic acid, 248 
Sulphates, 89, Q2 

in urine, 356 
Sulphids, 87 
Sulphites, 88 

Sulphocyanates in saliva, 309, 310, 318 
Sulphocyanic acid, 229 
Sulphones, 245 
Sulphonic acids, 244 
Sulphuric ether, 205 
Sulphur iodid (for blow pipe test), 101 
Sulphur test, 183 
Supraredalin, 165 
Sweet spirits of nitre, 208 
Sylvite, 69 
Symbols, denned, 2 
Symmetrical hydrocarbons, 241 
Syntonin, 278, 291 

T. 

Talcum, 63 
Tannic acid, 176 
Tannin, 176 
Tartar, 178 

analysis of, 179 

composition of, 179 

emetic, 32, 221 
Tartaric acid, 221 
Taurine, 223, 245 
Taurocholic acid in bile, 338 
Teeth, analysis of, 179 

and tartar, 178 
Temporary alloy, 117 
Tertiary alcohols, 196, 197 
Teichmann's haemin crystals, 296 

test (Exp. 206), 299 
Thein, 235 
Thermometers, 8 
Thioalcohol, 245 
Thiocyanate in saliva, determination, 

3i8 
Thiocyanic acid, 229 
Thiosulphates, 88 

Thorner, on acidity of milk, Ref., 287 
Thrombase, 294 
Thrombin, 294 
Thymol, 176, 243 
Thymophen, 176 
Tin, 33 

alloys, 33 

amalgams, 115 

cement, 123 

chlorid, preparation of, 34 



Tin, gravimetric determination of, 154 
Tinstone, 1^ 
Titration, denned, 143 
Tollen's reagent, 201 

test for aldehyd (Exp. 64), 201 
Toluene, 241 
Toluol, 241 
Tribrommethane, 192 
Tribromphenol, 174 

microchemical crystals, 162 
Trichloracetic acid, 176, 214 
Trichloraldehyd, 199 
Trichlormethane, 191, 168 
Tricresol, 246 
Trihydroxybenzene, 243 
Tri-iodomethane, 192 
Trimethylamine, 226 
Trimethyl-benzene, 242 
Trimethyl-xanthin, 235 
Trinitro-cellulose, 265 
Trinitro-phenol, 246 

preparation of (Exp. 117), 251 
Triolein, 209 
Trioxymethylene, 198 
Trioxypurin, 234 
Tripalmitin, 209 

Triple bonded hydrocarbons, 190 
Tristearin, 209 
Tritenyl, 208 
Tropa-cocaine, 177 
Tropaeolin, 335 
Truedentalloy, 117 
Trypsin, 337 
Trypsinogen, 337 
Twentieth Century alloy, 117 
Type metal, 109 
Tyrosin, 223, 248 

preparation of, 377 (also Exp. 231), 

339 

U. 
Uffelmann's reagent, 335 
Ultimate analysis, 182 
Unorganized ferments, 253 
Unsaturated hydrocarbons, 189 
Unsymmetrical hydrocarbons, denned, 

241 
Uranium, standard solution, 153 
Urates, deposit of, 369 
Urea, 232 

and H 2 (reaction), 232 
and NaBrO (reaction), 233 
Urease, 255 

Urea determined by Doremus Hinds 
apparatus, 350 
by Ferris's apparatus (saliva), 320 



402 



INDEX 



Urea determined by Squibb 's apparatus, 

349 
in saliva, 312 
qualitative test for, 348 
nitrate, 233 
oxalate (microchemical crystals), 162, 

233 
Urea (synthesis of Ex. 99), 238 
Ureas, substituted, 234 
Ureids, defined, 234 
Uric acid, 235, 350 

and lithium salts, 237 

and Na 2 HP0 4 , 237 

determination, 351 
Cook's method, 351 
Folin's method, 352 
Hopkin's method, 352 

in tartar, 179 

proportion to urea, 368 
Urinary sediments, 367 
Urine, abnormal constituents, 358 

acetone in, 364 

albumin in, 358 

alkaline phosphates in, 355 

ammonia in, 352 

analyses, 373 to 376 inc. 

analysis, interpretation of, 372 

appearance of, 345 

bile in, 365 

causes of cloudy, 345 

chlorin in, 353 

coloring matter in, 356 

epithelium in, 370 

indoxyl in, 357 

normal solids in, 348 

phosphates in, 355 

physical properties of, 344 

reaction and specific gravity of, 346 

sulphates in, 356 
Urinometers, 346 
Urobilin, 356, 357 
Urochrome, 357 
Uroerythrin, 357 
Uro-rosein, 357 

V. 

Valence, 2 

Valeric acid, 213, 214 

Vaseline, 187 

Vegetables, oxalic acid in, 218 

Verdigris, 22 

Vinegar, 213 

determination of strength, 144 
test for malic acid (Exp. 90), 224 

Viscosity of saliva, 315 



Vitellin, 275 

Volatile alkali, 78 

Volumetric analysis, 137 

determinations {see individual sub- 
stances), 142 to 153 inc. 

Volumetric methods for saliva and 
urine, 150 

W. 

Washing soda, 72 

Water, detection of, in alcohol (Exp. 58), 

199 
Water of ammonia, 76 
Waxy casts, 371 
Weldon's process for chlorin, 52 
White arsenic, 26 
White blood corpuscles, 296 

lead, 18 

precipitate, 23, 24 

vitriol, 54 
Will and Varrentrap's test for nitrogen, 

183 
Wilson, Dr. G. H., expansion of plaster, 

Ref., 62 
Witherite, 60 

Wohler's test for nitrogen, 183 
Wood's metal, 126 
Wood spirit, 197 
Wrought iron, 43 



X. 



Xanthin, 235, 236 
Xanthoproteic test, 277 
Xylene, 241 
Xylol, 241 
Xylose, 258 



Yeast, 253 
Yellow wash, 23 



Z. 



Zein, 282 

Zinc, 53 

Zinc alloys, 54 

amalgams, 115 
Zincates, 55 
Zinc blende, 53 

carbonate, 54 

ferrocyanide, 55 

gold solder, 129 

gravimetric determination of, 156 

hydrate, 55 

in dental alloy, 116 

lactate, 220 



INDEX 403 

Zinc oxalate, 55 Zinc, separation from manganese, 56 
oxychlorid, 122 sulphate, 54 

oxyphosphate, 120 sulphid, 54 

oxysulphate, 123 volumetric determination of, 151 

peroxid, 169 white, 54 

sarcolactate, 220 Zymogens, 254 



NOV 9 1912 



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